Carrier 68G5-105 Series, MCI J4500 COACH Operation & Service Manual

Carrier
Transicold

Transport
Air Conditioning

68G5-105 SERIES
MCI J4500 COACH

T-312 Rev-

Operation
&Service

OPERATION AND
SERVICE MANUAL

TRANSPORT

AIR CONDITIONING

EQUIPMENT

Model 68G5--105 Series

MCI J4500 Model Coach

Carrier Transport Refrigeration and Air Conditioning,
A member of the United Technologies Corporation family. Stock symbol UTX.
Carrier Transicold, Carrier Corporation, P.O. Box 4805, Syracuse, N.Y . 13221 U. S. A.

2003 CarrierCorporation D Printed in U. S. A. 0903

for

SAFETY SUMMARY

GENERAL SAFETY NOTICES

The following general safety notices supplement the specific warnings and cautions appearing elsewhere in
this manual. They are recommended precautions that must be understood and applied during operation and
maintenance of the equipment covered herein. The general safety notices are presented in the following three
sections labeled: First Aid, Operating Precautions and Maintenance Precautions. A listing of the specific
warnings and cautions appearing elsewhere in the manual follows the general safety notices.

FIRST AID

An injury, no matter how slight, should never go unattended. Always obtain first aid or medical attention
immediately.

OPERATING PRECAUTIONS

Always wear safety glasses.
Keep hands, clothing and tools clear of the evaporator and condenser fans.

No work should be performed on the unit until all circuit breakers and start-stop switches are turned off, and
power supply is disconnected.

Always work in pairs. Never work on the equipment alone.
In case of severe vibration or unusual noise, stop the unit and investigate.

MAINTENANCE PRECAUTIONS

Beware of unannounced starting of the evaporator and condenser fans. Do not open the condenser fan grille
or evaporator access panels before turning the power off, and securing the power source.

Be sure power is turned off before working on motors, controllers, solenoid valves and electrical control
switches. Tag circuit breaker and power supply to prevent accidental energizing of circuit.

Do not bypass any electrical safety devices, e.g. bridging an overload, or using any sort of jumper wires.
Problems with the system should be diagnosed, and any necessary repairs performed, by qualified service
personnel.

When performing any arc welding on the unit, disconnect all wire harness connectors from the modules in the
control box. Do not remove wire harness from the modules unless you are grounded to the unit frame with a
static-safe wrist strap.

In case of electrical fire, open circuit switch and extinguish with CO

(never use water).

2

Safety - 1 T312

SPECIFIC WARNINGS AND CAUTIONS

WARNING
BE SURE TO OBSERVE WARNINGS LISTED IN THE SAFETY SUMMARY IN THE FRONT OF
THIS MANUAL BEFORE PERFORMING MAINTENANCE ON THE HVAC SYSTEM

WARNING
DO NOT USE A NITROGEN CYLINDER WITHOUT A PRESSURE REGULATOR

WARNING
DO NOT USE OXYGEN IN OR NEAR A REFRIGERATION SYSTEM AS AN EXPLOSION MAY

OCCUR.

WARNING
EXTREME CARE MUST BE TAKEN TO ENSURE THAT ALL THE REFRIGERANT HAS BEEN
REMOVED FROM THE COMPRESSOR CRANKCASE OR THE RESULTANT PRESSURE WILL
FORCIBLY DISCHARGE COMPRESSOR OIL.

WARNING
WHEN MOVING THE COIL CARE MUST BE TAKEN TO AVOID PERSONAL INJURY BE­CAUSE OF THE WEIGHT OF THE COIL.

CAUTION
Do not under any circumstances attempt to service the microprocessor. Should a problem
develop with the microprocessor, replace it.

CAUTION
Care Must Be Taken To Ensure That The Manifold Common Connection Remains Immersed
In Oil At All Times Or Air And Moisture Will Be Drawn Into The System.

CAUTION
To prevent trapping liquid refrigerant in the manifold gauge set be sure set is brought to

suction pressure before disconnecting.

T-312

Safety - 2

TABLE OF CONTENTS

Section Page

SAFETY SUMMARY i........................................................................

DESCRIPTION 1-1..........................................................................

1.1 INTRODUCTION 1-1................................................................

1.2 GENERAL DESCRIPTION 1-2........................................................

1.2.1 Condenser Assembly 1-2.........................................................

1.2.2 Compressor Assembly 1-4........................................................

1.2.3 Evaporator Assemblies 1-4.......................................................

1.2.4 Main Control Box 1-7.............................................................

1.2.5 System Operating Controls And Components 1-8....................................

1.2.6 Other Carrier Supplied Items 1-9...................................................

1.3 REFRIGERATION SYSTEM COMPONENT SPECIFICATIONS 1-9........................

1.4 ELECTRICAL SPECIFICATIONS - WOUNDFIELD MOTORS 1-9.........................

1.5 ELECTRICAL SPECIFICATIONS-MAIN CONTROLLER INPUT SENSORS AND

TRANSDUCERS 1-9................................................................

1.6 SAFETY DEVICES 1-10.............................................................

1.7 HEATING (ENGINE COOLANT) FLOW CYCLE 1-11....................................

1.8 AIR CONDITIONING REFRIGERANT CYCLE 1-12......................................

1.9 ELECTRONIC AUTOMATIC CONTROL DATA FLOW 1-14...............................

OPERATION 2-1............................................................................

2.1 STARTING, STOPPING AND OPERA TING INSTRUCTIONS 2-1.........................

2.1.1 Operating Controls 2-1...........................................................

2.1.2 HVAC Power to Controller 2-2.....................................................

2.1.3 Starting 2-2.....................................................................

2.1.4 Activating Defrost 2-3............................................................

2.1.5 Setting RAM (Fresh) Air 2-3.......................................................

2.1.6 Active Alarm 2-3.................................................................

2.1.7 Diagnostics (Parameters) 2-3.....................................................

2.1.8 Stopping 2-3....................................................................

2.2 PRE-TRIP INSPECTION 2-3.........................................................

2.3 SYSTEM DESCRIPTION 2-3.........................................................

2.3.1 Pull Up and Pull Down Modes 2-3..................................................

2.3.2 Bypass Heat valve Control 2-5....................................................

2.3.3 Auxiliary Heater Control 2-5......................................................

2.3.4 Humidity Control 2-5.............................................................

2.3.5 Compressor Unloader Control 2-5..................................................

2.3.6 Passenger Area Evaporator Fan Speed Selection 2-5................................

2.3.7 Driver’s Area Evaporator Fan Speed Selection 2-5...................................

2.3.8 Condenser Fan Speed Control 2-5.................................................

2.3.9 Staging 2-6.....................................................................

2.3.10 Compressor Clutch Control 2-6....................................................

2.3.11 RAM Air Control 2-6.............................................................

2.3.12 Startup 2-6.....................................................................

2.3.13 Input Processing 2-6.............................................................

2.3.14 Self Tests 2-6...................................................................

i

T-312

TABLE OF CONTENTS -- Continued

Section Page

2.3.15 Alarm Description 2-6............................................................

2.3.16 Hour Meters 2-6.................................................................

2.3.17 Communications (Driver Display - Controller) 2-6....................................

TROUBLESHOOTING 3-1....................................................................

3.3.1 System Will Not Cool 3-5.........................................................

3.3.2 System Runs But Has Insfficient Cooling 3-5........................................

3.3.3 Abnormal Pressures 3-5..........................................................

3.3.4 Abnormal Noises Or Vibrations 3-5.................................................

3.3.5 Control System Malfunction 3-6....................................................

3.3.6 No Evaporator Air Flow Or Restricted Air Flow 3-6...................................

3.3.7 Expansion Valve Malfunction 3-6...................................................

3.3.8 No Or Insufficient Heating 3-6.....................................................

SERVICE 4-1...............................................................................

4.1 MAINTENANCE SCHEDULE 4-1......................................................

4.2 SUCTION AND DISCHARGE SERVICE VAL VES 4-1....................................

4.3 INSTALLING MANIFOLD GAUGES 4-2................................................

4.3.1 Installing R-134a Manifold Guage Set 4-2...........................................

4.4 PUMPING THE SYSTEM DOWN OR REMOVING THE REFRIGERANT CHARGE 4-2......

4.4.1 System Pumpdown 4-2...........................................................

4.4.2 Removing the Refrigerant Charge 4-3..............................................

4.4.3 Refrigerant Removal From An Inoperative Compressor. 4-3...........................

4.4.4 Pump Down An Operable Compressor For Repair 4-3................................

4.5 REFRIGERANT LEAK CHECK 4-4....................................................

4.6 EVACUATION AND DEHYDRATION 4-4...............................................

4.6.1 General 4-4.....................................................................

4.6.2 Preparation 4-4..................................................................

4.6.3 Procedure for Evacuation and Dehydrating System 4-4...............................

4.7 ADDING REFRIGERANT TO SYSTEM 4-6.............................................

4.7.1 Checking Refrigerant Charge 4-6..................................................

4.7.2 Checking Refrigerant Charge (Alternate Method) 4-6.................................

4.7.3 Adding Full Charge 4-6...........................................................

4.7.4 Adding Partial Charge 4-6........................................................

4.8 CHECKING FOR NONCONDENSIBLES 4-6...........................................

4.9 CHECKING AND REPLACING HIGH PRESSURE CUTOUT SWITCH 4-7..................

4.9.1 Replacing High Pressure Switch 4-7................................................

4.9.2 Checking High Pressure Switch 4-7................................................

4.10 FILTER-DRIER 4-7..................................................................

4.10.1. To Check Filter Drier 4-7..........................................................

4.10.2. To Replace Filter Drier 4-7........................................................

4.11 THERMOSTATIC EXPANSION VALVE 4-7.............................................

4.11.1 Replacing the Expansion Valve 4-7.................................................

4.11.2 To Check/Measure Superheat 4-8..................................................

iiT-312

TABLE OF CONTENTS -- Continued

Section Page

4.12 MODEL 05G COMPRESSOR MAINTENANCE 4-8......................................

4.12.1 Removing the Compressor 4-8....................................................

4.12.2 Re--installing the Compressor 4-9..................................................

4.12.3 Compressor Unloaders 4-9.......................................................

4.12.4 Compressor Oil Level 4-10........................................................

4.12.5 Adding Oil with Compressor in System 4-10.........................................

4.12.6 Adding Oil to Service Replacement Compressor 4-10.................................

4.12.7 Removing Oil from the Compressor: 4-10...........................................

4.13 TEMPERATURE SENSOR CHECKOUT 4-11...........................................

4.14 HUMIDITY SENSOR CHECKOUT 4-11................................................

4.15 SUCTION AND DISCHARGE PRESSURE TRANSDUCER CHECKOUT 4-11...............

4.16 REPLACING SENSORS AND TRANSDUCERS 4-12....................................

4.17 SERVICING MAIN EVAPORATOR BLOWER ASSEMBLY 4-12...........................

4.18 ACCESSING MAIN EVAPORATOR MOTOR BRUSHES 4-12.............................

4.19 SERVICING MOTOR BRUSHES 4-12.................................................

4.20 SERVICING THE MAIN EVAPORATOR AND HEATER COIL 4-13.........................

4.21 REMOVING THE CONDENSER ASSEMBLY 4-13......................................

4.22 SERVICING THE CONDENSER COIL 4-13............................................

4.23 SERVICING THE CONDENSER MOTOR 4-13..........................................

4.24 SERVICING THE DRIVER CONTROL BOX 4-13........................................

4.25 SERVICING THE DRIVER EVAPORATOR 4-14.........................................

4.25.1 Access Cover Removal 4-14......................................................

4.25.2 Blower Removal 4-14............................................................

4.25.3 Air filter Removal 4-14............................................................

4.25.4 Removal of Evaporator/Heater Coil Assembly 4-14...................................

4.25.5 RAM Air Actuator Removal 4-14...................................................

4.26 SERVICING THE PARCEL RACK EVAPORATOR 4-14..................................

4.26.1 Motor Removal 4-14.............................................................

4.26.2 Removal of Parcel Rack Evaporator Coil 4-14.......................................

ELECTRICAL SCHEMATIC DIAGRAMS 5-1....................................................

5.1 INTRODUCTION 5-1................................................................

LIST OF ILLUSTRATIONS

Figure Page

1-1. Coach Cutaway View 1-1.................................................................

1-2. Condenser Assembly 1-2.................................................................

1-3. Compressor Assembly 1-3................................................................

1-4. Driver Evaporator Assembly 1-5...........................................................

1-5. Parcel Rack Evaporator 1-5...............................................................

1-6. Main Evaporator Assembly 1-6............................................................

1-7. Main Control Box 1-7.....................................................................

1-8. System Operating Controls (upper left hand switch panel) 1-8.................................

1-9. Parcel Rack On/Off 1-8...................................................................

1-10. Driver A/C 1-9..........................................................................

1-11. Heating System Flow Diagram 1-11.......................................................

iii

T-312

LIST OF ILLUSTRATIONS -- Continued

Figure Page

1-12 Air Conditioning Refrigerant Flow Diagram 1-13.............................................

1-13. Electronic Automatic Control Data Flow Block Diagram 1-14..................................

2-1. System Operating Controls (upper left hand switch panel) 2-1.................................

2-2. Parcel Rack On/Off 2-2...................................................................

2-3. Driver A/C 2-2...........................................................................

2-4. Main Controller Automatic Control Sequence 2-4............................................

4-1. Suction or Discharge Service Valve 4-1....................................................

4-2. Manifold Gauge Set (R--134a) 4-2.........................................................

4-3. Compressor Service Connections 4-3......................................................

4-4. Refrigerant Service Connections 4-5.......................................................

4-5. Checking High Pressure Switch 4-7........................................................

4-6. Thermostatic Expansion Valve 4-7.........................................................

4-7. Thermostatic Expansion Valve Bulb and Thermocouple Installation 4-8.........................

4-8. Removing Bypass Piston Plug 4-9.........................................................

4-9. Model O5G Compressor 4-9..............................................................

4-10.Removing Driver Control Box 4-13........................................................

5-1. Electrical Schematic Diagram Legend and Symbols 5-2......................................

5-2. Electrical Schematic Diagram 5-3.........................................................

5-3. Electrical Schematic Diagram 5-4.........................................................

5-4. Electrical Schematic Diagram 5-5.........................................................

LIST OF TABLES

Tab le Page

1-1. Part (Model) Number Chart 1-1............................................................

1-2. Additional Support Manuals 1-1............................................................

1-3. Safety Devices (Within Carrier Supplied Equipment) 1-10.....................................

2-1. Main Evaporator Fan Speed Relay Operation 2-5............................................

2-2. Main Area Staging 2-6....................................................................

3-1. Microprocessor Error Message Definition 3-1................................................

3-2. Display Error Message Definition 3-1.......................................................

3-3. Driver Display Panel Alarm Message Definition 3-1...........................................

3-4. Parameter Codes 3-4....................................................................

3-5. General System Troubleshooting Procedures 3-5............................................

4-1. Checking Refrigerant Charge 4-6..........................................................

4-2. Checking Refrigerant Charge 4-6..........................................................

4-3. T emperature Sensor(AT, TSC, TSD and TSR) Resistance 4-11................................

4-4. Humidity Sensor (HS) Voltage 4-11.........................................................

4-5. Suction and Discharge Pressure Transducer (SPT and DPT) Voltage 4-12.......................

4-6. R-134a Temperature - Pressure Chart 4-15..................................................

ivT-312

SECTION 1

DESCRIPTION

1.1 INTRODUCTION

heater, a driver evaporator with integral heater, optional

parcel rack evaporators, compressor assembly, main
This manual contains Operating and Service
Instructions and Electrical Data for the Model 68G5-105

Coach Air Conditioning and Heating equipment
furnished by Carrier Transicold Division for the MCI
J-Series Intercity coach. Table 1-1 provides a model
number chart.

The Model 68G5-105 equipment (see Figure 1-1)
consist of a condenser, a main evaporator with integral

control box, driver display panel, check valve assembly,

temperature sensors and a bypass heat valve.

The 68G5 air conditioning and heating equipment

interfaces with electrical cabling, a parcel rack

evaporator thermostat kit, refrigerant piping, engine

coolant piping, ductwork and other components

furnished by the coach manufacturer to complete the

system.

Table 1-1. Part (Model) Number Chart

Model No. Refrigerant Controller Fan Motors Parcel Rack Connection

68G5-105

R-134a

Microprocessor 24VDC Yes

Table 1 -2. Additional Support Manuals

MANUAL/FORM NUMBER EQUIPMENT COVERED TYPE OF MANUAL

62--02756 O5G Compressor Operation and Service

T--200PL O5G Compressor Parts List
T--279PL MCI E/J Coach Parts List

Driver Evaporator

Driver Display
Panel

*Driver Evaporator

Control Box

Parcel Rack Evaporator

Main Control Box

Condenser

Roadside Return Air
Temperature Sensor

*INDICATES COMPONENTS FURNISHED

BY THE COACH MANUFACTURER

*Bypass

Heat
Val ve

Main Evaporator

Curbside Return Air
Temperature and
Humidity Sensor

Check
Val ve

Compressor
Assembly

Figure 1 -1. Coach Cutaway View

1-1

T-312

1.2 GENERAL DESCRIPTION

1.2.1 Condenser Assembly

The condenser assembly (See Figure 1-2) includes a
condenser coil, fan and motor assemblies, filter-drier,
sight glass, control box, liquid line solenoid valve(s),
king valves and an ambient temperature sensor.

The condenser coil provides a heat transfer surface for
condensing refrigerant gas at a high temperature and
pressure into a liquid at high temperature and pressure.
The condenser fans circulate ambient air across the
outside of the condenser tubes at a temperature lower
than refrigerant circulating inside the tubes; this results
in condensing the refrigerant into a liquid. The filter-drier
removes moisture and other noncondensibles from the
liquid refrigerant before it enters the thermal expansion
valves in the evaporator assemblies.

The condenser is also fitted with a fusible plug which
protects the system from unsafe high temperatures.
The control box includes condenser fan relays no. 1 and
no. 2 (CFR1 and CFR2) to enable the main controller to
control operation of condenser fan motors no. 1 and no.
2 (CM1 and CM2). The control box also includes
condenser speed relay no. 1 (CSR1) which controls the
speed of both condenser fan motors CM1 and CM2. The
main evaporator liquid line solenoid valve and the parcel
rack liquid line solenoid valve (when so equipped)
closes when the system is shut down to prevent
refrigerant migration and to isolate the filter-drier for
servicing when the compressor is shut down. The king
valves enable servicing of the condenser assembly. The
ambient temperature sensor measures ambient
temperature and sends an electrical signal to the main
controller.

16827

435

91011

14

19

20

1. Condenser Coil Assembly

2. Fusible Plug

3. Liquid Line Outlet Fitting (Parcel Rack)

4. Liquid Line Outlet Fitting (Main)

5. Model/Serial No. Nameplate

6. Fan Guard

7. Filter-Drier

8. Venturi Ring

9. Condenser Fan Motor CM1

10. Fan Blade
1 1. Condenser Fan Motor CM2

15161718 13

13 Control Box--Contains: Condenser Fan

Relay No.1 (CFR1), Condenser Fan Relay
No. 2 (CFR2) and Condenser Speed Relay
No. 1 (CSR1)

14. Moisture & Liquid Indicator

15. Control Box Positive (+) Stud

16. Control Box Positive (+) Stud

17. Control Box Negative (--) Stud
18 Liquid Line (King) Valve

19. Discharge Shutoff King Valve

20. Refrigerant Inlet Fitting

12. Outside Temperature Sensor

12

T-312

Figure 1 -2. Condenser Assembly

1-2

87654321

4

9

24

23

2

4

ROADSIDE VIEW

22

DRIVE END VIEW

CURBSIDE VIEW

19

18 17 16 15 14 13

21

20

PUMP END VIEW

1

TOP VIEW

1. Suction Pressure Transducer
2 Bracket, Belt Guard

3. Weatherpack Clutch Coil Connector

4. Electric Solenoid Unloader

5. Discharge Valve Connection, Size 16 ORS

6. Discharge Service Valve

7. Discharge Valve Charging Port

8. O–Ring

9. Oil Drain Plug

10. Solenoid Unloader Electric Connectors

11. High Pressure Switch

12. Discharge Pressure Transducer

13. Capscrew

14. Lockwasher

15. Special Washer

16. Lock Nut

17. Key

18. Suction Valve Charging Port

19. Suction Service Valve

20. Clutch Assembly

21. Oil Fill Plug

22. Oil Level Sightglass

23. Suction Valve Connection, Size 24 ORS

24. O–Ring

10

11

12

Figure 1-3. Compressor Assembly

1-3

T-312

1.2.2 Compressor Assembly

The compressor assembly (See Figure 1-3.) includes
the refrigerant compressor, clutch assembly, suction
and discharge service valves, high pressure switch,
suction and discharge pressure transducers, suction
and discharge servicing (charging) ports and electric
solenoid unloaders.

The compressor raises the pressure and temperature of
the refrigerant gas and forces it into the condenser
tubes. The clutch assembly provides a means of belt
driving the compressor by the coach engine. The
suction and discharge service valves enable servicing
of the compressor. Suction and discharge access
(charging) ports mounted on the service valves enable
connection of charging hoses for servicing of the
compressor, as well as other parts of the refrigerant
circuit. Transducers convert refrigerant pressures into
electrical signal inputs which are sent to the main
controller. The high pressure switch (HPS) is a normally
closed switch, its contacts open on a pressure rise to
shut down the system when abnormally high refrigerant
pressures occur. The electric unloaders provide a
means of controlling compressor capacity , which
enables control of temperature inside the coach. For
more detailed information on the compressor, refer to
manual number 62-02756.

1.2.3 Evaporator Assemblies

The evaporator assemblies include a driver evaporator
assembly (See Figure 1-4), a main evaporator
assembly (See Figure 1-6), and may include two parcel
rack evaporator assemblies (See Figure 1-5).

The driver evaporator assembly includes an evaporator
coil assembly, a thermal expansion valve, a heater coil
assembly, an evaporator heat valve (EHV), two fan and

motor assemblies, an air filter, and two condensate
drain connections. The evaporator heat valve (EHV) for
the driver evaporator is installed in the piping outside the
evaporator assembly. In addition, the driver evaporator
has an actuator, which controls the outside (RAM) air
damper upon receipt of signal from the main controller.

The main evaporator assembly includes an evaporator
and heater coil assembly, a thermal expansion valve, an
evaporator heat valve (EHV), a fan and motor assembly,
an air filter, and two condensate drain connections.
There is also an evaporator speed fan relay (EFRL),
which changes main evaporator fan speed upon receipt
of a signal from the main controller.

The optional parcel rack evaporator assemblies
includes an evaporator coil assembly, a thermal
expansion valve, a fan and motor assembly,
condensate drain connection, and a return air
thermostat (on the road side only).

The evaporator coils provide a heat transfer surface for
transferring heat from air circulating over the outside
surface of the coil to refrigerant circulating inside the
tubes; thus providing cooling when required. The
thermal expansion valves meter the flow of refrigerant
entering the evaporator coils. The heating coils provide
a heat transfer surface for transferring heat from engine
coolant circulating inside the tubes to air circulating over
the outside surface of the tubes, thus providing heating
when required. The evaporator heat valve(s) (EHV)
controls the flow of engine coolant supplied to the
heating coils. The fans circulate the air over the coils.
The air filters filter dirt particles from the air before the air
passes over the coils. The condensate drain
connections provide a means for disposing of
condensate collected on the evaporator coils during
cooling operation.

T-312

1-4

2

31

5

4

6

16

15

14

13

1. Access Panel

2. Electrical Connector

3. Nameplate

4. Air Bleed Valve

5. Fan and Motor

6. Solenoid Valve and Coil

7. Thermal Expansion Valve

8. RAM Actuator

Figure 1-4. Driver Evaporator Assembly

12

13

11

9. RAM Air Door

10. Liquid Inlet Connection, Size 11/16 ORS
1 1. Suction Outlet Connection, 1-7/16 ORS

12. Service Port

13. Condensate Drain Connections

14. Air Filter

15. Evaporator Coil Assembly

16. Heater Coil Assembly

7

8

9

10

3

2
1

1. Suction Outlet Connection

2. Liquid Inlet Connection

3. Side Access Panel

4. Top Access Panel

5. Thermal Expansion Valve

6. Evaporator Coil Assembly

7654

8

11

7. Fan and Motor

8. Motor Mount Bracket
9 Condensate Drain Connection

10. Relay
1 1. Thermostat (Not supplied by Carrier)

Figure 1-5. Parcel Rack Evaporator Assembly

1-5

9

10

T-312

20

19

18

17

16

15

31

4

52

14 13 12 67

10

11 9

1. Thermal Expansion Valve

2. Refrigerant Liquid Inlet Connection, 3/8“ ORS

3. Evaporator/Heater Coil Assembly

4. Heater Coil Inlet Connection, 7/8 OD

5. Evaporator Heat Valve (EHV)

6. Blower Housing, Right

7. Blower Wheel, Right

8. Nameplate

9. Evaporator Fan Relay, High Speed (EFRH)

10. Evaporator Fan Relay, Low Speed (EFRL)
1 1. Elastomeric Motor Mounts

12. 2-Speed Motor

13. Blower Wheel, Left

14. Blower Housing, Left

15. Service Port

16. Coolant Drain valve

17. Heater Coil Outlet Connection, 7/8 OD

18. Capillary Tube and Bulb (TXV)

19. Refrigerant Suction Outlet Connection, 1” ORS

20. Air Bleed Valve

21. Air Filter Channel

8

21

Figure 1-6. Main Evaporator Assembly

T-312

1-6

1.2.4 Main Control Box

The main control box (See Figure 1-7) includes a main
controller (microprocessor module), expansion output
board, receptacle, quick connectors, connectors and
fuses (F2 and F3). The main controller (microprocessor
module) contains the electronic hardware to measure
inputs and process the outputs to automatically control

the air conditioning and heating system to maintain

temperatures inside the coach. The microprocessor

section has a built in memory facility for checking proper

operation; this includes checks of the program memory,

data memory and analog. It has a self test feature which

is executed when the system is first powered up. The

expansion board drives six discrete outputs in addition

to the standard outputs from the controller.

20

18 17 16

1110987654321

1312

20

21

14

15

19

1. Connector (MA)

2. Connector (MB)

3. (Not Used)

4. Fuse (F2)

5. (Not Used)

6. Fuse (F3)

7. (Not Used)

8. Quick Connector (QC1)

9. Connector (KA)

10. Connector (KB)
1 1. Connector (MA)

12. Quick Connector (QC2)

13. Connector (MB)

14. Relay

15. Expansion Board

16. Main Controller

17. Packard Connector Pins L thru Y

18. Packard Connector Pins A thru K

19. Coach Interface Connector

20. Model/Serial Number Plate (Box)

21. Model/Serial Number Tag (Controller)

Figure 1 -7. Main Control Box

1-7

T-312

Defrost (Driver’s
Evap Blower)

Display

Up (Increase) Selection

Down (Decrease) Selection

Automatic Control

Vent Only

Cooling
Only

DEF

H

I

G

H

L
O
W

HEAT

H

I
G
H

L
O

W

Heat (Driver’s Evap
Coolant Valve)

Figure 1-8. System Operating Controls

(upper left hand switch panel)

1.2.5 System Operating Controls And
Components

There are five controls on the driver’s station which
affect the operation of the Carrier supplied equipment
covered by this manual. These controls include two
rocker switches, two slide switches, and the Micromate
Control Panel.

On/Off

Fresh Air Heat Only

Inside/Outside

Fan Speed

Tem p e ra t u re

temperature reaches the desired set point, the system
will maintain compressor operation and open the heat
valve to allow reheating of the return air. In the reheat
mode interior temperature is maintained at the desired
set point while additional dehumidification takes place.

The first slide switch is the Defrost Switch (Figure 1-8).
This switch controls the driver evaporator blower motor
speed. The second slide switch is the Heat Switch
(Figure 1-8). This switch controls the driver evaporator
coolant valve. These switches are located on the
dashboard to the left of the steering wheel.

The third control is the Driver Display Panel (Figure 1-8)
which operates the Carrier Transicold microprocessor
controller, circuit breakers and relays. Modes of
operation include Vent, Heat, Cool and Auto. This
control panel is located on the dashboard with the slide
switches to the left of the steering wheel.

In the vent mode the evaporator fans are operated to
circulate air in the bus interior.

In the heat mode the heat valve and the OEM supplied
floor blower and/or boost pump are energized. The
evaporator fans operate to circulate air over the
evaporator coil and heater coil in the same manner as
the vent mode.

In the cooling mode the compressor is energized while
the evaporator and condenser fans are operated to
provide refrigeration as required. The compressor is
fitted with cylinder unloaders to match compressor
capacity to the bus requirements. Once the interior

Figure 1-9. Parcel Rack On/Off

The forth control is the rocker switch for the Parcel Rack
(Figure 1-9). This switch will de--activate the parcel rack
evaporators if the main evaporator is in operation. This
switch is located on the dashboard to the right of the
steering wheel.

The fifth control is the rocker switch for the Driver A/C
(Figure 1-10). It is located on the left side console panel
near the transmission gear selector. This switch will
activate the system to provide cooling for the driver in
the event that cooling is not called for by the Carrier
Transicold microprocessor.

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1-8

Figure 1-10. Driver A/C

1.2.6 Other Carrier Supplied Items

Other Carrier supplied items include curbside and
roadside return air temperature sensors, two coolant
control valves and a check valve. The temperature
sensors provide input to the controller on temperature
conditions in the coach. The bypass heat (coolant
control) valve provides a path for coolant flow when all
evaporator heat valves are closed. The other coolant
control valve is the heat valve that controls the flow of
coolant to the driver heater coil. The check valve is
installed in the compressor refrigerant discharge line
and allows refrigerant flow in only one direction to
prevent liquid return to the compressor when the
compressor is shut down.

1.3 REFRIGERATION SYSTEM COMPONENT
SPECIFICATIONS

a. Refrigerant Charge

R-134a: 17.5 lb (8 kg)

b. Compressor

Model: 05G
No. of Cylinder: 6
Weight (Dry): 145 lb (66 kg) including clutch
Oil Charge:

New Compressor: 5.8 pints (2.7 liters)
Replacement Compressor: 5.5 pints (2.6 liters)

Oil Level:

Level in sight glass between bottom of glass and
middle of glass on compressor crankcase
(curbside)

Approved Compressor Oils - R-134a:

Castrol: Icematic SW68C
Mobil: EAL Arctic 68
ICI: Emkarate RL68H

c. Thermostatic Expansion Valve - for R-134a

Units:

1. Main Evaporator:

Superheat Setting (Nonadjustable): 12 to 18_F

(6.7 to 10.1_C)

MOP Setting: None

2. Driver Evaporator and Parcel Rack
Evaporator:

Superheat Setting (Nonadjustable): 5 to 12_F

(6.7 to 10.1_C)

MOP Setting: None

d. High Pressure Switch (HPS):

Opens at: 385 10 psig (26.2  . 68 BAR)
Closes at: 285 10 psig (19.39  .68 BAR)

1.4 ELECTRICAL SPECIFICATIONS - WOUND
FIELD MOTORS

a. Main Evaporator/Heater Blower (Fan) Motor

Bearing Lubrication: Factory Lubricated (additional

grease not required)

Horsepower:

High Speed: 1.6 (1.2 kw)
Low Speed: 0.7 (0.5 kw)

Full Load Amps (FLA):

High Speed: 56
Low Speed: 28

Operating Speed:

High Speed: 1550 rpm
Low Speed: 1200 rpm

Voltage: 24 vdc

b. Driver Evaporator/Heater Blower (Fan) Motor

Bearing Lubrication: Factory Lubricated (additional

grease not required)
Full Load Amps (FLA): 9.5
Operating Speed:

High Speed: 3300 rpm

Medium Speed: 1600 rpm

Low Speed: 1100 rpm
Voltage: 24 vdc

c. Condenser Fan Motor

Bearing Lubrication: Shell Dolium R
Horsepower: 0.8 hp (1.072 kw)
Full Load Amps (FLA):

High Speed: 32

Low Speed: 21
Operating Speed:

High Speed: 1800 rpm

Low Speed: 1600 rpm
Voltage: 24 vdc

d. Parcel Rack Evaporator Fan Motor

Bearing Lubrication: Factory Lubricated (additional

grease not required)
Full Load Amps (FLA): 9.5
Operating Speed: 3300 rpm
Voltage: 24 vdc

1.5 ELECTRICAL SPECIF ICATIONS-MAIN
CONTROLLER INPUT SENSORS AND
TRANSDUCERS

a. Suction and Discharge Pressure Transducer

Supply Voltage: 4.5 to 5.5 vdc (5 vdc nominal)
Input Range: --6.7 to 450 psig (--0.05 to 30.62 BAR)
Output Voltage: vdc = 0.0098 x psig

+ 0.4659 (See Table 4-5 for calculations.)

b. Temperature Sensors

Input Range: --52.6 to 158_F (--47 to 70_C)
Output: NTC 10K ohms at 77_F (25_C)

(See Table 4-3 for calculations.)

1-9

T-312

1.6 SAFETY DEVICES

System components are protected from damage
caused by unsafe operating conditions with safety
devices. Safety devices that are connected to Carrier
Transicold supplied equipment include a high pressure
switch (HPS), fuses (See T able 1-3.) and a fusible plug.

In addition, evaporator and condenser fan motors and
the main control box are protected independently
against high current draw by circuit breakers suppliedby
the coach manufacturer. The evaporator and condenser
fan motors are also protected from high temperature
with internal thermal protection switches. If a condenser
fan motor safety device opens to stop the condenser fan
motor(s), the system may develop a high pressure
condition, which may open the high pressure switch
(HPS) to shut the unit down.

a. Pressure Switches

High Pressure Switch (HPS)

The high pressure switch (HPS) is installed in the
compressor center cylinder head and opens on a
pressure rise to shut down the system when high
pressure conditions occur. (Refer to: 1.3.d.)

Table 1-3. Safety Devices (For Carrier Supplied Equipment)

Unsafe Condition Safety Device Device Setting

High compressor discharge

High Pressure Switch (HPS) Refer to 1.3.d.

pressure

Excessive current draw by the

Fuse (F2) Opens at 5 amps

controller 12 vdc supply circuit

Excessive current draw by the

Fuse (F3) Opens at 10 amps

controller 24 vdc output circuit

During the A/C mode, HVAC system operation will
automatically stop if the HPS switch contacts open due
to an unsafe operating condition. Opening HPS
contacts de-energizes, through the main controller, the
A/C compressor clutch and condenser fan relays
shutting down the system.

b. Fuses

Fuses (F2 and F3)

Fuse (F2), internal to the controller, protects the
controller 12 vdc supply circuit from excessive current
draw. Fuse (F3) protects the controller 24 vdc output
circuit from excessive current draw.

c. Thermal Switches

Condenser Motor Overloads (CMOL1 and CMOL2)

Each condenser fan motor is equipped with an internal
thermal protector switch, condenser motor overloads
(CMOL1 and CMOL2). If excessive motor temperature
exists, the CMOL switch will open to de-energize the
corresponding condenser fan relay (CFR1 or CFR2);
this will stop the affected condenser motor.

T-312

1-10

1.7 HEATING (ENGINE COOLANT) FLOW CYCLE

Heating circuit components furnished by Carrier
Transicold include heater cores and evaporator heat
valves (EHV) for the driver and main evaporator
assemblies and a coolant bypass heat valve.
Components furnished by the coach manufacturer
include auxiliary heater and engine water pump,
auxiliary heater, hand valves and “Y” type strainers. The

main controller automatically controls the EHV valves
during heating and reheat cycles to maintain required
temperatures inside the coach. Engine coolant (glycol
solution) is circulated through the heating circuit by the
engine and auxiliary water pumps. When the evaporator
heat valve solenoid is de-energized, the valve will open
to allow engine coolant to flow through the heater coil.
(See Figure 1-11.) The valve is normally open so that if a
failure occurs, the system will still be able to supply heat.

*HAND VALVE

*’Y’ STRAINER

*AUXILIARY

HEATER

HEAT
VALVE

DRIVER
HEATER
CORE

HEAT
VALVE

MAIN
HEATER CORE

BYPASS HEAT VALVE

AIR BLEED

VALVE

AIR BLEED

VALVE

DRAIN VALVE

*HAND VALVE

*ENGINE

WATER PUMP

*ENGINE

*INDICATES COMPONENTS FURNISHED

BY THE COACH MANUFACTURER

Figure 1-11. Heating System Flow Diagram

1-11

T-312

1.8 AIR CONDITIONING REFRIGERANT CYCLE

When air conditioning (cooling) is selected by the main
controller, the unit operates as a vapor compression
system using R-134a as a refrigerant. The main
components of the system are the reciprocating
compressor, air-cooled condenser coil, subcooler,
filter-drier, thermostatic expansion valves, liquid line
solenoid valves and evaporator coils. (See Figure 1-12)

The compressor raises the pressure and the
temperature of the refrigerant and forces it through the
discharge line, and the check valve into the condenser
tubes. The condenser fan circulates surrounding air
(which is at a temperature lower than the refrigerant)
over the outside of the condenser tubes. Heat transfer is
established from the refrigerant (inside the tubes) to the
condenser air (flowing over the tubes). The condenser
tubes have fins designed to improve the transfer of heat
from the refrigerant gas to the air; this removal of heat
causes the refrigerant to liquefy.

The refrigerant leaves the condenser and then flows
through the subcooler, which subcools the refrigerant
before it enters the thermal expansion valves; this
reduces flash gas in the evaporator. From the
subcooler, the liquid refrigerant passes through the
liquid line (King) service valve, and then through a
filter-drier where an absorbent keeps the refrigerant
clean and free of water.

From the filter-drier, the liquid refrigerant then flows
through the main liquid line solenoid valve to the main
evaporator and thermal expansion valve and to the

parcel rack evaporator solenoid valve (if this option is
active) the parcel rack thermal expansion valve and
through the driver solenoid valve (if this option is active)
and to the driver thermal expansion valve. The solenoid
valves open during cooling to allow refrigerant to flow to
the thermal expansion valves. The main liquid solenoid
valve and the parcel rack liquid line solenoid valve
(when so equipped) closes during shutdown to prevent
refrigerant migration. The thermal expansion valves
reduce the pressure and temperature of the liquid and
meters the flow of liquid refrigerant to the evaporator to
obtain maximum use of the evaporator heat transfer
surface.

The low pressure, low temperature liquid that flows into
the evaporator tubes is colder than the air that is
circulated over the evaporator tubes by the evaporator
blower (fan). Heat transfer is established from the
evaporator air (flowing over the tubes) to the refrigerant
(flowing inside the tubes). The evaporator tubes have
aluminum fins to increase heat transfer from the air to
the refrigerant; therefore the cooler air is circulated to
the interior of the coach.

The transfer of heat from the air to the low temperature
liquid refrigerant in the evaporator causes the liquid to
vaporize. This low temperature, low pressure vapor
passes through the suction line and returns to the
compressor where the cycle repeats.

When ventilation only is selected by the main controller,
only the evaporator fans function to circulate air
throughout the coach. The refrigerant cycle will remain
off.

T-312

1-12

DRIVER SOLENOID
VALVE

Discharge
Liquid

Suction

CONDENSER
ASSEMBLY

MAIN LIQUID LINE
SOLENOID VALVE

CONDENSER

PARCEL RACK
LIQUID LINE
SOLENOID VALVE

FILTER

DRIER

SIGHT-­GLASS

TXV

DRIVER EVAPORATOR
ASSEMBLY

TXV

MAIN EVAPORATOR ASSEMBLY

PARCEL EVAPORATOR
ASSEMBLY

TXV

TXV

TXV BULB

SERVICE PORT

TXV BULB

SERVICE
PORT

SERVICE
PORT

SUBCOOLER

DISCHARGE LINE
SERVICE VALVE

SERVICE PORT

FUSIBLE
PLUG

DISCHARGE LINE

LIQUID LINE (KING)
SERVICE VALVE

DISCHARGE
CHECK VALVE

COMPRESSOR

PARCEL EVAPORATOR

ASSEMBLY

SUCTION LINE

Figure 1 -12 Air Conditioning Refrigerant Flow Diagram

SERVICE
PORT

1-13

T-312

1.9 ELECTRONIC AUTOMATIC CONTROL DATA
FLOW

The system is supplied with 12 and 24 vdc power from
the coach power supply. The main controller receives
input from pressure transducers, temperature sensors,
condenser and evaporator fan motor overloads, high
pressure switch, fuses. It then processes these inputs to
control output devices enabling automatic control of

12 /24 VDC
POWER
SUPPLY

temperature conditions inside the coach. The driver
display provides a communication link between the
main controller and the rest of the system. The following
block diagram (Figure 1-13) indicates data flow through
the system. Refer to section 2 for more detailed
information on the theory of operation of the control
system and see section 5 for system electrical
schematics.

24 VDC
POWER
SUPPLY

INPUT
DEVICES
(Transducers,
Sensors and
HP switch)

12 VDC
POWER
SUPPLY

DRIVER
DISPLAY

OUTPUT
DEVICES

MAIN CONTROLLER

(Solenoids,

Relays,
Clutch)

EXPANSION

BOARD

OUTPUT DEVICES
(Heater Solenoid
Valves and RAM Air
Actuators)

MAIN CONTROL BOX

24 VDC
POWER
SUPPLY

Figure 1 -13. Electronic Automatic Control Data Flow Block Diagram

Fan Motors,
Compressor,
Driver Control
Box

T-312

1-14

SECTION 2

OPERATION

HEAT

(a.)

(b.)

Down (Decrease) Selection

On/Off

(1.)

Defrost (Driver’s Evap Blower)

Driver Display Panel (c.)

DEF

H

I
G
H

L
O

W

H

I
G
H

L
O

W

Heat (Driver’s Evap Coolant Valve)

Display

Figure 2-1. System Operating Controls

(upper left hand switch panel)

2.1 STARTING, STOPPING AND OPERATING
INSTRUCTIONS

2.1.1 Operating Controls

There are five operating controls (Figure 2-1) used to
control the functions of this system. They are as follows:

a. The Defrost Switch controls the driver evaporator

blower motor speeds. With this switch the driver con­trols the amount of air discharged to the windshield.
This function is independent of any other HVAC func­tion in the coach.

b. The Heat Switch controls the coolant valve to the driv-

er’s evaporator. With this switch the driver controls
the amount of engine coolant flowing thru the driver’s
evaporator heater core, hence increasing or decreas­ing the temperature of air that is discharged to the
windshield. This function is independent of any other
HVAC function in the coach.

c. The Driver Display Panel controls the Carrier Trans-

icold microprocessor controller which in turn controls
the operation of the heating and air conditioning sys­tem. With this control the driver controls the tempera­ture of air to the passenger area and cooling to the
driver area. The panel has 10 keys whose functions
are described as follows:

1. On/Off -- Pressing this key will change the display

state from inactive to active. If the controller is active
the display will illuminate and the other keypad LEDs
will be active.

Automatic Control

Up (Increase) Selection

Inside/Outside
Temperature

(2.)

(3.)

Fresh Air

(8.)

Vent Only

(9.)

Fan Speed

(6.)

Heat Only

2. Up (Increase Selection) -- If the set point is displayed
when the Up key is pressed, the display will increase
set point 1_F (0.5_C).

3. Down (Decrease Selection) -- If the set point is dis­played when the Down key is pressed, the display
will decrease set point 1_F (0.5_C).

4. Auto (Auto Control Selection) -- Pressing the Auto
button illuminates the AUTO LED and signals the
controller to automatically cycle to the control set
point. If the AUTO LED is illuminated, the manual
modes will be de--activated, the COOL, VENT, and
HEAT LED’s will not be illuminated.

5. Cool (Cool Mode Selection) -- If the COOL button is
pressed, the COOL LED is illuminated, the system
will only cool to control set point. The AUTO, VENT,
and HEAT LED’s will not be illuminated.

6. Vent (Ventilation Mode Selection) -- If the VENT but­ton is pressed, the VENT LED is illuminated, only the
system fans will operate. The AUTO, COOL, and
HEAT LED’s will not be illuminated.

7. Heat (Heat Mode Selection) -- If the HEAT button is
pressed, the HEAT LED is illuminated, the system
will operate in the heat mode only, cycling the coolant
control valves as needed to maintain set point. The
AUTO, COOL, and VENT LED’s will not be illumi­nated.

8. Inside/Outside Temperature -- After start--up, the
display shows set point. The temperature display
selection button will toggle the display to show bus

(4.)

Cooling
Only

(7.)

(10.)

(5.)

2-1

T-312

inside or outside temperature. The inside tempera­ture is obtained by averaging the curb and road side
return air sensors (located in the return air ducts). If
one sensor is not functioning the display will read
only the functioning sensor, if both are not function­ing, the display will show ’--40’. The outside temper­ature sensor is located in the condenser assembly.

When the key is toggled to display the inside temper­ature, the inside LED will be illuminated. When the
key is toggled to display the outside temperature, the
outside LED will be illuminated. When the key
toggles to show set point, both inside and outside
LEDs are turned off.

9. Fresh Air -- The Fresh Air Button has two selection
LEDs, Fresh Air and Circulation. If the fresh air
damper door is open, the Fresh Air LED is illumi­nated, if the fresh air damper door is closed, the Cir­culation LED will be illuminated.

After start-- up, the fresh air selection is in AUTO, the
controller will control the fresh air damper door.
When the key is toggled the damper selection will
move to the next step an Auto--Closed--Open--Auto
sequence. The Auto selection allows controller to
operate the damper, the Closed or Open being the
closed or open damper door selections with the
damper door held in those respective positions until
the button is toggled again.

10.Fan Speed -- After start--up, the display obtains the
the current fan speed status from the controller. If the
controller is in AUTO no fan speed LEDs will be illu­minated. When a fan speed is selected the appropri­ate LED will be illuminated.

11. _F/_C -- Key combination is used to select _For_C.
When the display is showing temperature, press and
hold the Inside/Outside Temperature selection
key(8.) and press the UP key(2.), the display will
show in the _F scale. When the display is showing
temperature, press and hold the Inside/Outside
Temperature selection key(8.) and press the DOWN
key(3.), the display will show in the _C scale.

Figure 2-2. Parcel Rack On/Off

d. The Parcel Rack Switch (Figure 1-9) controls the liq-

uid line solenoid valve and the blower motors of the
parcel rack evaporators. The driver controls the par­cel rack evaporator function with this switch. The par­cel rack evaporators will function only after the main
evaporator is operating.

Figure 2 -3. Driver A/C

e. The Driver A/C Switch (Figure 2-3) allows the driver

to control cooling with the driver’s evaporator. When
the switch is in AUTO, the driver’s area cooling is
controlled by the microprocessor controller. When
the switch is in COOL, the driver’s area is demanding
cooling, even if the microprocessor is calling for heat­ing in the passenger area.

2.1.2 HVAC Power to Controller

Before starting the system, electrical power must be
available from the coach power supply.

2.1.3 Starting

The Driver Display Panel consists of a display and a
keypad (Figure 2-1), which allows the user to modify
and observe system operating parameters.

On start--up a self test will execute. While the test is
being executed the display will show its programing
revision number in the format of X.X, where X is a digit
from 1 to 9 (ex. 1.4). At his time three possible error
messages may also appear on the display. Refer to
Table 3-2 for definitions.

a. If the engine is not running, start the engine. The

HV AC system will restart in the AUTO mode. All sys­tem controls will operate automatically in heating,
cooling or ventilating mode, as required.

b. CONTROL PANEL (Figure 2-1)

It is suggested the system be started in the automatic
mode.

1. The Driver Display Panel may be programmed to
display the set point temperature or return air tem­perature. To determine which display temperature is
programmed, press the TEMPERATURE button so
that the OUT SIDE AIR indicator is illuminated. If the
controller cycles back to the INSIDE AIR indicator,
than the controller is programmed to display return
air temperature. If the controller does not automati­cally cycle back to the return air indicator, than the
controller is programmed to display set point temper­ature.

2. The Control Panel will signal the controller to perform
start up when the ON/OFF button is pushed. Ensure
the AUTO button indicator is illuminated. If not, press
the AUTO button to place the system in the automat­ic mode.

3. If cooling only, heating only or ventilation only is de­sired, press the corresponding button (refer to
Figure 2-1) to illuminate the indicator light and manu­ally place the system in that mode of operation.

4. If low or high speed evaporator fan speed is desired,
press the FAN SPEED button to illuminate the indi­cator light and bring speed to the desired level.

T-312

2-2

5. To open or close the fresh air damper, press the
FRESH AIR button.

6. To read interior or exterior temperature, press the
TEMPERATURE button to illuminate the indicator
light and bring the display to the desired temperature
reading. After a short delay, the display will return to
the default set point or return air temperature read­ing.

7. Setpoint may be changed by pressing the UP or
DOWN arrow button. The UP button will increase the
setpoint temperature and the DOWN button will de­crease the setpoint temperature.

2.1.4 Activating Defrost

2.1.8 Stopping

With the system operating, pressing the ON/OFF key
will stop the HVAC system operation and the display will
be blank.

2.2 PRE-TRIP INSPECTION

After starting system operation, allow system to
stabilize for ten to fifteen minutes and check for the
following:

a. Listen for abnormal noises in compressor or fan mo-

tors.

b. Check compressor oil level. (Refer to paragraph

4.12.4)

Windshield defrost is initiated and controlled with the
Defrost switch and the Heat switch (Figure 2-1). Moving
the switches to the high setting on both will deliver the
highest volume of warm air on the windshield.
Correspondingly, moving either or both of the two
switches to the low setting will decrease the volume of
air and the temperature of air delivered across the
windshield.

2.1.5 Active Alarm

During normal operation, the controller monitors system
operating parameters for out of tolerance conditions.
The display gets the controller alarm queue information
every 30 seconds. Alarms will be shown as an alarm
code. If an alarm is activated and the display is reading
temperature, the display will show the temperature and
the alarm code alternately in 1 second intervals.

2.1.6 Diagnostics (Check for Alarms)

If an alarm condition exists, diagnostics can be manually
initiated to isolate system fault(s) by simultaneously
pressing the Up and Down Selection keys continuously
for five seconds. Diagnostics should be accessed only
when the coach is not moving. When entering the
diagnostic mode, all LEDs for the key pad will be turned
off. All keys except the On/Off, Up (increase) Selection
and Auto keys will stop functioning. T o scroll through
the diagnostic information press the UP key. Pressing
the O/I key at any time will exit this mode. To clear the
alarm message, scroll thru the alarms until ’------’
appears, then press the Auto Key for 5 seconds or until
’------’ disappears. Refer to section 3 for description of
diagnostics. Refer to Table 3-3 for definition of alarm
messages.

2.1.7 Diagnostics (Parameters)

To access the system parameters press the Up and
Down Selection keys continuously for five seconds. The
display will now be in the Diagnostics mode and may be
displaying alarms. Scroll thru the alarms(if present) until
’------’ appears. With ’-- -- --’ displayed on the read--out,
press the Up Selection key. The first parameter code
will be displayed. To scroll thru the parameters press the
Up Selection key. When showing parameters, the
display will first flash out the parameter identifier Pxx for
one second and then show the parameter value. To
return to normal operation press the On/Off key (see
Figure 2-1). Refer to Section 3 for for definitions of the
parameter codes.

c. Check refrigerant level. (Refer to paragraph 4.7.1)

d. Ensure that self-test has been successfully per-

formed and that there are no errors or alarms indi­cated. (Refer to paragraph 2.1.5 or 2.1.6)

2.3 SYSTEM DESCRIPTION

Refer to Section 5 for sample schematic diagrams of the
power and control circuits.

2.3.1 Pull Up and Pull Down Modes

At power up, the system will enter a pull up or pull down
mode to rapidly obtain desired temperatures within the
coach. During this mode, the system will run at
maximum heating or cooling capacity until the set point
(in the passenger zone) is reached for the first time. For
the driver zone, temperature control is controlled by the
two slide switches next to the controller (See
Figure 2-1).

1. Pullup/pulldown main evaporator fan speed is limit­ed to a maximum of thirty minutes and can be put in
pullup/pulldown speed only once. When the control­ler switches out of pullup/pulldown speed, pullup/
pulldown speed is prevented again by the controller
unless the controller is shut off and restarted. The
display cannot override the fan speed to pullup/pull­down.

2. The minimum run time in pullup or pulldown for the
main evaporator fans is three minutes for automatic
control.

a. Capacity State Selection

The main controller automatically compares system
temperature with the controller set point and changes
system operating modes at certain temperature
deviations. Figure 2-4 shows various changes in
operating modes and controller actions at various
temperature deviations from controller set point. Upon
rising temperature, mode changes occur at values in
Figure 2-4 above controller set points, On a falling
temperature, mode changes occur when temperatures
are equal to those given in Figure 2-4 The system will
operate in these modes unless pressure overrides the
controller settings. If the controller detects that the
temperature setting is not being reached during a period
of time, it will slowly adjust the temperature at which
these modes are entered; this will allow the system to
always attempt to reach the controller temperature
setting.

2-3

T-312

COOLING MODE
HIGH SPEED MAIN EVAP FAN
COMPR FULLY LOADED (6 CYL)

COOLING MODE
COMPR FULLY LOADED (6 CYL)

EVAPORATOR

RETURN AIR TEMP

ABOVE SET POINT

____F (4.75____ C)

8.5

8 _

_F(4.5 ____C)

__

closing the heating valve. The compressor clutch and
condenser fan motors are energized as appropriate.

Reheat allows for both net cooling and net heating by
varying the time that the heat valve is open. The time is
automatically calculated by the controller and is based
on a 20 second period.

c. Heating

In the heat capacity state, the liquid solenoid valve is
closed to stop cooling and the compressor will shut
down. The heating capacity can then be varied by
adjusting the time the heat valve is open. The time is
automatically calculated by the controller and is based
on a 20 second period.

COOLING MODE
LOW SPEED MAIN EVAP FAN
COMPR FULLY LOADED (6 CYL)

COOLING MODE
LOW SPEED MAIN EVAP FAN
COMPR SEMI-LOADED (4 CYL)

REHEAT MODE
HUMIDITY LESS THAN 49%
LOW SPEED MAIN EVAP FAN
COMPR UNLOADED (2 CYL)

OR

HUMIDITY CONTROL MODE
HUMIDITY GREATER TAN 50%
HIGH SPEED MAIN EVAP FAN
COMPR FULLY LOADED (6 CYL)

HEAT MODE
LOW SPEED MAIN EVAP FAN
COMPR FULLY UNLOADED
(CLUTCH DISENGAGED)

HEAT MODE
COMPR FULLY UNLOADED
(CLUTCH DISENGAGED)

HEAT MODE
HIGH SPEED MAIN EVAP FAN
COMPR FULLY UNLOADED
(CLUTCH DISENGAGED)

6.75 _

_F(3.75 ____C)

__

5.5 _

_F(3.0 ____C)

__

SET POINT

-- 3 . 5 _F(-- 2 . 0 _C)

-- 8 _

_F(-- 4 . 5 ____C)

__

-- 8 . 5 _

_F(--4.75 ____C)

__

d. Driver Area Control

The Driver’s A/C switch on the left side console is turned
on when cooling is desired in the driver area.

The driver area conditions are controlled by manually
adjusting the Defrost and Heat slide switches on the
dash board. These controls operate in conjunction with
the main coach controller. Temperature control is ac­complished by regulating the flow of engine coolant
through the heating coil in the driver evaporator (with the
Heat slide switch) by controlling a normally open electric
solenoid valve. The volume of air flow directed about the
driver area is controlled (with the Defrost slide switch) by
the speed of the drivers evaporator fan motors.

The heating coil reheats the precooled air to maintain
the desired temperature at the set point. During heat­ing, the driver area liquid solenoid valve is closed and
the heating valve is opened and closed for a percentage
of the heat valve period.

e. Passenger Area Control

The passenger area temperature is controlled by
maintaining the return air temperature as measured by
the return air sensors located at the rear of the coach in
the return air ducts. The return air sensors are averaged
together to provide input for the controller.

FALLING
TEMP.

RISING
TEMP.

For humidity control refer to 2.3.4

Figure 2-4. Main Controller Automatic Control

Sequence

b. Cooling/Reheat

Cooling and reheat require various combinations of
evaporator fan speeds and compressor unloading.
Cooling is accomplished by energizing the compressor
and condenser, opening the liquid solenoid valve and

T-312

If cooling is required for the passenger area, the
compressor and condenser will start and the main liquid
line solenoid valve is opened and the heat valve is
closed.

During reheat, the main liquid solenoid valve is opened
and the heating valve is opened and closed for a
percentage of the heat valve period (20 seconds).

To enter the heat mode for the passenger area, the
controller must be calling the heat valve to be cycling at
51% or higher. If this condition is not met, the area
requiring heat is put into reheat. During heating, the
main evaporator liquid solenoid valve is closed and the
heating valve is opened and closed for a percentage of
the heat valve period (20 seconds). Once the heat mode
has been entered, the controller will not re--enter heat
until the heat valve has closed to less than 25%.

2-4

2.3.2 Bypass Heat Valve Control

The normally open Bypass Heat Valve is closed on
system start--up. During re--heat, the bypass heat valve
remains closed when the heat valves are open, and
opens 2 seconds before the heat valves close (to
prevent water hammering).

2.3.3 Auxiliary Heater Control

The auxiliary heater output is energized when the heat
valve has been opened 100% for 60 seconds. Once
energized, the auxiliary heater output is de--energized
when the heat valve percentage is less than 20 percent
for fifteen minutes.

The OEM supplied Auxiliary Heater Switch located on
the left side console can independently energize the
auxiliary heater when the engine is off. When placing
the switch in the ON position, the switch activates the
auxiliary heater for a timed period of 90 minutes.
Placing the switch in the OFF position or starting the
coach engine will de--activate the auxiliary heater.

2.3.4 Humidity Control

Humidity control (reheat mode) is activated when the
humidity is greater than fifty percent and the passenger
zone temperature is less than 5_F(3_C) above set
point. When these conditions are met the compressor
will be fully loaded (6 cylinders)and at the same time the
heat valve(s) will cycle open to maintain temperature.
Once humidity control is activated, it will remain
activated until the humidity is less than 45 percent or the
return air temperature drops 2_F(1_C) below set point.

2.3.5 Compressor Unloader Control

The unloader outputs control the capacity of the
compressor by energizing or de-energizing unloader
solenoid valves. Energizing a valve solenoid
de-activates a pair of compressor cylinders. The 05G
compressor has six cylinders. Four cylinders are
equipped with two sets of unloader valves (UV1 and
UV2), each controlling two cylinders; this allows the
compressor to be operated with two, four or six
cylinders. When the compressor is off, the unloader
solenoids are de-energized immediately .

Whenever the compressor is changed from off to on, the
unloaders are forced energized for fifteen seconds.
After fifteen seconds, one unloader solenoid may be
de-energized, if required. Any subsequent changes
between energizing and de-energizing the unloader
solenoids must be staged with a thirty second delay.
Only one unloader may change state at a time when
staging is required.

a. Suction Pressure

In addition to temperature control, the electric unloaders
will be used to prevent coil frosting. Staging is ignored
for energizing the unloader solenoid due to suction
pressure overrides :

1. Compressor Unloader Bank 1 Solenoid (UV1).
When the suction pressure decreases below 25 psig
(1.7 BAR), the first unloader solenoid is energized
unloading the first compressor cylinder bank (two

cylinders); this output will remain energized until the
pressure increases to above 32 psig (2.18 BAR).

2. Compressor Unloader Bank 2 Solenoid (UV2).
When the suction pressure decreases below 21 psig
(1.43 BAR), the second unloader solenoid is ener­gized unloading the second compressor cylinder
bank (two cylinders); this output will remain ener­gized until the pressure increases to above 28 psig
(1.91 BAR).

b. Discharge Pressure

Head Pressure is also controlled by the unloaders.
Staging is ignored for energizing the unloader solenoid
due to discharge pressure overrides :

1. Compressor Unloader Bank 1 Solenoid (UV1).
When the discharge pressure increases above 340
psig (23.13 BAR), the first compressor unloader so-
lenoid is energized; this output will remain energized
until the pressure decreases below 300 psig (20.41
BAR).

2.3.6 Passenger Area Evaporator Fan Speed

Selection

The passenger area evaporator assembly is equipped
with a two speed fan motor. Temperature control is the
primary method of determining the fan speed selection.
Table 2-1 indicates relay operational status for the
various fan motor states.

Table 2 -1. Main Evaporator Fan Speed Relay

Operation

STATE

HIGH SPEED

RELA Y

LOW SPEED

RELA Y

Off Off Off

Low On On

High On Off

Pull

Up/Down

On Off

2.3.7 Driver’s Area Evaporator Fan Speed

Selection

The driver air conditioning unit is equipped with two
evaporator fan motors. The Defrost slide switch
determines the fan speed. See (Figure 2-1).

2.3.8 Condenser Fan Speed Control

The first condenser fan motor (CM1) is energized when
the compressor clutch output is energized.

The second condenser fan motor (CM2) is energized
when the clutch is energized and the discharge
pressure increases above 175 psig (1.2 mkPa). It will be
de-energized when the clutch is de-energized or the
discharge pressure decreases below 125 psig (0.861
mPa).

The condenser fans are started in low speed and will
remain in low speed until the discharge pressure
increases above 225 psig (1.6 mPa). The fans will
remain in high speed until the discharge pressure
decreases below 165 psig (1.1 mPa).

2-5

T-312

2.3.9 Staging

When the system is started, the fans are staged on to
reduce the total starting current. There is no staging
required for the driver evaporator fan motors, as they
start immediately. Staging for the evaporator and
condenser fan motors are given in the Table 2-2.

Table 2 -2. Main area Staging

Ref.

Time

(seconds)

Controller Action

Time 0 0 Main Evaporator Fan Low

Time 2 Time0+2 Main Evaporator Fan High

Time 3 Time0+4 Condenser Fan 1 Low

Time 4 Time3+1 Condenser Fan 2 Low

Time 5 Time3+3 Both Condenser Fans High

2.3.10 Compressor Clutch Control

A belt driven electric clutch is employed to transmit en­gine power to the air conditioning compressor. De-ener­gizing the clutch electric coil disengages the clutch and
removes power from the compressor. The clutch will be
engaged whenever any area is calling for cooling. The
clutch will be disengaged when the system is off, when
all areas are in heating or during high and low pressure
conditions. The clutch coil is controlled by the main con­troller.

The clutch coil is prevented from engagement when the
ambient temperature is below 32_F (0_C).

The clutch coil will be de-energized if the discharge
pressure rises to 350 psig (2.4 mPa), the setting of the
compressor mounted high pressure switch. The clutch
coil will energize when the discharge pressure falls to
240 psig (1.7 mPa).

The clutch coil will be de-energized if the suction press­ure decreases below 6 psig (41 kPa).

2.3.11 RAM Air Control

The RAM air control regulates admission of outside air
into the system.

a. Display Override

The RAM air can be automatically controlled or set to
open or closed by the display .

b. RAM Air Auto Mode

1. If the passenger return air temperature is greater
than controller set point plus 2_F (1.1_C) or less than
set point minus 2_F (1.1_C), the RAM air will be
closed.

2. Otherwise, RAM air is open.

An exception to the above is that there is a five minute
delay to open RAM air once it is closed in the auto mode.
There is no delay to close RAM air.

2.3.12 Startup

At startup, the controller will power on and perform all
power up tests.

2.3.13 Input Processing

The system determines correct operation by reading
temperature sensors (thermistors), pressure
transducers and the humidity sensor. Refer to section

1.5 for electrical specifications for input devices and

sections 1.2.1, 1.2.2 and 1.2.6 for functional
descriptions.

2.3.14 Self Tests

With the engine running, self tests are automatically
executed.

“ER5” indicates a data memory failure. “ER6” indicates
a program memory failure. If any of these or any other
errors are displayed on the screen, proceed to
Table 3-1.

2.3.15 Alarm Description

Alarm descriptions and troubleshooting procedures are
provided in section 3.

2.3.16 Hour Meters

An hour meter records the compressor run time in
hours. The maximum reading is 999,999.

An Hourmeter records the total elapsed time the
controller has been on in hours. The maximum reading
is 999,999.

2.3.17 Communications (Driver Display -

Controller)

The controller uses communications to transmit data to
the display. The communications link is RS232.

T-312

2-6

SECTION 3

TROUBLESHOOTING

CAUTION
Do not under any circumstances attempt to service the microprocessor. Should a problem develop
with the microprocessor, replace it.

NOTE

To access LED display on the microprocessor, remove cover
from main control box located in rear of electrical compartment.

Table 3-1. Microprocessor Error Message Definition

ERROR

CODE

0 1secon-1secoff Not Applicable as system is operating normally.

1 1 flash - 5 sec pause Record error code number, tag and replace the mi croprocessor.

2 2 flashes - 5 sec pause Record error code number, tag and replace the mi croprocessor.

3 3 flashes - 5 sec pause Record error code number, tag and replace the mi croprocessor.

4 4 flashes - 5 sec pause Record error code number, tag and replace the mi croprocessor.

5 5 flashes - 5 sec pause Record error code number, tag and replace the mi croprocessor.

6 6 flashes - 5 sec pause Record error code number, tag and replace the mi croprocessor.

STATUS OF

LED DISPLAY

REMEDY

Table 3-2. Display Error Message Definition

ERROR

CODE

Er4 Communications Failure If the display does not receive data from the microprocessor.

Er5 Data Memory If memory on the display is not verified on power up.

Er6 Program Memory If program memory on the display is not verified on power up by a checksum.

ALARM

NO.

A11 Main Left

MESSAGE MESSAGE DEFINITION

Table 3-3. Driver Display Panel Alarm Message Definition

TITLE CAUSE REMEDY MICROPROCESSOR RESPONSE

Probe Failure

Sensor is unplugged,
wiring defective or
main left evaporator
return air temperature
sensor failure.

Ensure sensor is

plugged in. Check

sensor resistance or

wiring. Replace sen-

sororrepairwiring.

(Refer to section 4.13

Switches to the right probe. If both
probes are bad, the microprocessor
will run in the full reheat and evapo­rator fans will operate on low speed.
The compressor will operate on six
cylinders if pressures permit.

and Table 4-3.)

A12 Main Right

Probe
Failure

Sensor is unplugged,
wiring defective or
main right evaporator
return air temperature
sensor failure.

Ensure sensor is

plugged in. Check

sensor resistance or

wiring. Replace sen-

sororrepairwiring.

(Refer to section 4.13

Switches to the left probe. If both
probes are bad, the microprocessor
will run in the full reheat and evapo­rator fans will operate on low speed.
The compressor will operate on six
cylinders if pressures permit.

and Table 4-3.)

3-1 T-312

Table 3-3. Driver Display Panel Alarm Message Definition - Continued

ALARM

NO.

A14 Ambient

TITLE CAUSE REMEDY MICROPROCESSOR RESPONSE

Probe Failure

A15 Suction Press-

ure
Transducer
Failure

A16 Discharge

Pressure
Transducer
Failure

A17 Humidity

Transducer
Failure

A18 Fuse Blown

Alarm

Sensor is unplugged,
wiring defective or
ambient temperature
sensor failure.

Sensor is unplugged,
wiring defective or
suction pressure trans­ducer failure.

Sensor is unplugged,
wiring defective or
discharge pressure
transducer failure.

Sensor is unplugged,
wiring defective or
humidity transducer
failure.

Defective wiring or
coach power source de­fective. microprocessor
Internal fuse is blown.

Ensure sensor is
plugged in. Check
sensor resistance or
wiring. Replace sen­sor or repair wiring.
(Refer to section 4.13
and Table 4-3.)

Ensure sensor is
plugged in. Check
transducer voltage or
wiring. Replace sen­sor or repair wiring.
(Refer to section 4.15
and Table 4-5.)

Ensure sensor is
plugged in. Check
transducer voltage or
wiring. Replace sen­sor or repair wiring.
(Refer to section 4.15
and Table 4-5.)

Ensure sensor is
plugged in. Check
transducer voltage or
wiring. Replace sen­sor or repair wiring.
(Refer to section 4.14
and Table 4-4.)

Repair or replace
wiring or power
source. Replace Fuse.

Ignores ambient temperature and
does not lock out the compressor
and does not open driver RAM air in
AUTO mode.

Energizes unloaders.

Energizes unloaders.

If conditions allow, not including the
humidity set point/humidity sensor
condition, activates humidity control
(dehumidification). (See section

2.3.4.) Does not open passenger
RAM air in AUTO. (Refer to section

2.3.11.)

All microprocessor outputs are de­energized.

A19 Main

Evaporator
Fan Overload

A22 Condenser

Fan Overload

Main evaporator fan
overload.

Condenser fan over­loads

Refertosection3.3.6. No microprocessor response other

than alarm.

Refertosection3.3.3
and/or 3.3.4

If the compressor is energized and
the first condenser fan overload
opens, the microprocessor will ener­gize the second condenser fan in or­der to detect the first overload con­dition.

If, after energizing the second con­denser fan, the second condenser fan
overload opens, the compressor
clutch will de-energize for the mini­mum off time, since neither con­denser fan is operating.

3-2T-312

ALARM

NO.

TITLE CAUSE REMEDY MICROPROCESSOR RESPONSE

A22 Condenser

Fan Overload
(continued)

Table 3-3. Driver Display Panel Alarm Message Definition - Continued

Condenser fan over­loads

Refertosection3.3.3

and/or 3.3.4

If after energizing the second con­denser fan, the second condenser fan
overload does not open, the micro­processor will keep the first over­load alarm activated and leave the
compressor and second condenser
fan energized. (The second condens­er fan remains energized since at
least one condenser fan must be en­ergized when the compressor is en­ergized.)

A23 High Pressure

Discharge

High discharge
pressure.

A25 Out of Range If the system is con-

_F

A26 Low Voltage/

Load Shed

trolling within 9

(5_C) of setpoint for a
period of 15 minutes
and then fails to con­trol within 18_F
(10_C) for any reason
this alarm will be acti­vated.

Low coach voltage.
Coach 12 vdc battery
supply voltage
dropped below 12.6
vdc for 30 seconds.

Check discharge

pressure transducer

voltage, wiring or

cause of high dis-

charge pressure. (Re-

fertosection4.15and

Table 4-5 and/or sec-

tion 3.3.3.)

Refertosection3.3.1,

3.3.2 and/or 3.3.8 de-

pending on heating/

cooling requirements.

Check/repair alterna-

tor or coach power

supply.

If this alarm has not been activated
three times in 30-minutes, it de-en­ergizes the clutch for the minimum
off time and until the alarm is de-ac­tivated. Energizes the second con­denser fan at high speed. De-ener­gizes the rest of the system unless
heat is required.

If this alarm has been re-activated
three times in 30-minutes, it de-en­ergizes the rest of the system. The
system will operate only in the heat
mode until the alarm is reset via
communications.

No microprocessor response other
than alarm.

De-energizes all outputs except driv­er evaporator fan motor. (See section

2.1.2.)

3-3 T-312

ALARM

ControllerSoftwar

e

NO.

TITLE CAUSE REMEDY MICROPROCESSOR RESPONSE

A27 Low Pressure

Shutdown

Table 3-3. Driver Display Panel Alarm Message Definition - Continued

Low suction pressure. Check cause of low

suction pressure. (Re­fer to section 3.3.3.)

If alarm has been activated three
times in 30-minutes, the clutch will
be de-energized until the alarm is
de-activated.

If alarm has been activated three
times in 30-minutes, de-energizes
the rest of the system unless heat is
required. Runs the main evaporator
fan at low speed until alarm is reset.

A28 High Voltage Power 12 vdc source

voltage is greater than

Check, repair or re­place alternator.

All microprocessor outputs are de­energized.

17 vdc.

A29 Low Voltage Power 12 vdc source

voltage is less than 10

Repair or replace
wiring or alternator.

All microprocessor outputs are de­energized.

vdc.

A31 EEPROM Memory failure. Replace main micro-

processor at next ser-

Modifies out of range values to their
default values.

vice stop.

Table 3-4. Parameter Codes

CODE CODE NAME DESCRIPTION

P5 Suction Pressure This value is the suction pressure measured by the suction pressure transduc-

P6 Discharge Pressure This value is the discharge pressure measured by the discharge pressure

P20 Compressor Hours

P21 Compressor Hours

P22 Evaporator Hours

P23 Evaporator Hours

P30

P31

High

Low

High

Low

Controller Software
Version

er. If the sensor is shorted it will display CL If it is open circuited it will display
OP. NOTE: This value is not updated, it is the value at the time that the code
is accessed.

transducer. If the sensor is shorted it will display “CL” and if it is open circuited
it will display “OP”. NOTE: This value is not updated, it is the value at the time
that the code is accessed.

This is the number of hours of operation that the compressor has run with the
clutch energized. The reading is in thousands.

This is the number of hours of operation that the compressor has run with the
clutch energized. The reading is in hundreds, tens and ones.

This is the number (in thousands) of hours of operation with the evaporator
fans energized.

This is the number (in hundreds, tens and ones) of hours of operation with the
evaporator fans energized.

This is the software version of the logic board. The first two digits of the soft­ware revision are displayed. Ex. Revision XXYY XX is displayed after P30.

This is the software version of the logic board. The second two digits of the
software revision are displayed. Ex. Revision XXYY YY is displayed after P31.

3-4T-312

Table 3 -5. General System Troubleshooting Procedures

INDICATION/

TROUBLE

3.3.1 System Will Not Cool

POSSIBLE CAUSES

Compressor will not run V-Belt loose or defective

Clutch coil defective
Clutch malfunction
Compressor malfunction

Electrical malfunction Coach power source defective

Circuit Breaker/safety device open

3.3.2 System Runs But Has Insfficient Cooling

Compressor V-Belt loose or defective

Compressor valves defective

Refrigeration system Abnormal pressures

No or restricted evaporator air flow
Expansion valve malfunction
Restricted refrigerant flow
Low refrigerant charge
Service valves partially closed
Safety device open
Liquid solenoid valve stuck closed

3.3.3 Abnormal Pressures

High discharge pressure Refrigerant overcharge

Noncondensable in system
Condenser fan rotation incorrect
Condenser coil dirty

Low discharge pressure Compressor valve(s) worn or broken

Low refrigerant charge

REFERENCE

SECTION

Check
Check/Replace
Check/Replace

See Note.

Check/Repair

Check/Reset

Check

See Note.

3.3.3

3.3.6

3.3.7 and 4.11

3.3.7 and 4.11

4.5 and 4.7
Open

1.6

Check

4.4

4.8

Check

Clean

See Note.

4.5 and 4.7

High suction pressure Compressor valve(s) worn or broken See Note.
Low suction pressure Suction service valve partially closed

Filter-drier inlet valve partially closed
Filter-drier partially plugged
Low refrigerant charge
Expansion valve malfunction
Restricted air flow

Suction and discharge pressures

Compressor valve defective See Note.

Open

Check/ Open

4.10

4.5 and 4.7

3.3.7

3.3.6

tend to equalize when system is
operating

3.3.4 Abnormal Noises Or Vibrations

Compressor Loose mounting hardware

Worn bearings
Worn or broken valves
Liquid slugging
Insufficient oil
Clutch loose, rubbing or is defective
V-belt cracked, worn or loose
Dirt or debris on fan blades

Condenser or evaporator fans Loose mounting hardware

Defective bearings
Blade interference
Blade missing or broken

Check/Tighten

See Note.
See Note.

3.3.7

4.12.4
Check

Check/Adjust

Clean

Check/Tighten

Replace

Check

Check/Replace

3-5 T-312

Table 3 -5. General System Troubleshooting Procedures - Continued

INDICATION/

TROUBLE

3.3.5 Control System Malfunction

POSSIBLE CAUSES

Will not control Sensor or transducer defective

Relay(s) defective
Microprocessor malfunction

3.3.6 No Evapotator Air Flow Or Restricted Air Flow

Air flow through coil blocked Coil frosted over

Dirty coil
Dirty filter

No or partial evaporator air flow Motor running in reverse

Motor(s) defective
Motor brushes defective(main evaporator)
Evaporator fan loose or defective
Fan damaged
Return air filter dirty
Icing of coil
Fan relay(s) defective
Safety device open

3.3.7 Expansion V alve Malfunction

Low suction pressure with high
superheat

Low refrigerant charge
Wax, oil or dirt plugging valve orifice
Ice formation at valve seat
Power assembly failure
Loss of bulb charge
Broken capillary

Low superheat and liquid slugging
in the compressor

3.3.8 No Or Insufficient Heating

Superheat setting too low
Ice or other foreign material holding valve open

Insufficient heating Dirty or plugged heater core

Coolant solenoid heat valve(s) malfunctioning or plugged
Low coolant level
Coolant bypass heat valve open or malfunctioning
Strainer(s) plugged
Hand valve(s) closed
Water pumps defective
Auxiliary Heater malfunctioning.

No Heating Coolant solenoid heat valve(s) malfunctioning or plugged

Microprocessor malfunction
Pump(s) malfunctioning
Safety device open

NOTE: Refer to Model 05G Compressor Manual, Form No. 62-02756.

REFERENCE

SECTION

4.13, 4.15 or

4.14
Check
Check

Defrost coil

Clean

Clean/Replace

Check

Repair/Replace

4.18/4.19
Repair/Replace
Repair/Replace

Clean/Replace

Clean/Defrost

Check/Replace

1.6

4.5 and 4.7

4.6

4.6

4.11.1

4.11.1

4.11.1

4.11

4.6

Clean

Check/Replace

Check

Check/Replace

Clean

Open
Repair/Replace
Repair/Replace

Check/Replace

Replace

Repair/Replace

1.6

3-6T-312

SECTION 4

OPERATION

REFERENCE

SERVICE

WARNING

BE SURE TO OBSERVE WARNINGS LISTED IN THE SAFETY SUMMARY IN THE FRONT OF THIS
MANUAL BEFORE PERFORMING MAINTENANCE ON THE HVAC SYSTEM

NOTE

Following completion of all maintenance or service activities, the alarm queue should be cleared of any
original alarms and any alarms generated during service. Refer to paragraph 2.1.6

4.1 MAINTENANCE SCHEDULE

SYSTEM

ON OFF

a. Daily Maintenance

X

Pre-trip Inspection -- after starting
Check tension and condition of V-belt

X

b. Weekly Inspection

X

Perform daily inspection

X

Check condenser, evaporator coils and air filters for cleanliness

X

Check refrigerant hoses and compressor shaft seal for leaks

X

Feel filter-drier for excessive temperature drop across drier

c. Monthly Inspection and Maintenance

X

Perform weekly inspection and maintenance

X

Clean evaporator drain pans and hoses

X

Check wire harnesses for chafing and loose terminals

X

Check fan motor bearings

X

Check compressor mounting bolts for tightness

X

Check fan motor brushes

4.2 SUCTION AND DISCHARGE SERVICE
VALVES

The suction and discharge service valves (See
Figure 4-1) used on the compressor are equipped with
mating flanges for connection to flanges on the
compressor. These valves are provided with a double
seat and a gauge connection, which allows servicing of
the compressor and refrigerant lines.

Turning the valve stem counterclockwise (all the way
out) will backseat the valve to open the suction or
discharge line to the compressor and close off the
gauge connection. In normal operation, the valve is
backseated to allow full flow through the valve. The
valve should always be backseated when connecting
the service manifold gauge lines to the gauge ports.

Turning the valve stem clockwise (all the way forward)
will frontseat the valve to close off the suction or
discharge line to isolate the compressor and open the
gauge connection.

To measure suction or discharge pressure, midseat the
valve by opening the valve clockwise 1/4 to 1/2 turn.
With the valve stem midway between frontseated and
backseated positions, the suction or discharge line is
open to both the compressor and the gauge connection.

REFERENCE

paragraph

2.2
None

4.1.a
None

4.5

4.10

4.1.b
None
Replace/Tighten
None
None

4.19, 4.23

TO DISCHARGE OR
FROM SUCTION LINE

PORT TO
COMPRESSOR

ACCESS VALVE CAP

Service Valve
Frontseated
(clockwise)

VALVE STEM CAP

VALVE
STEM

ACCESS VALVE
(R-134a)

Service Valve
Backseated
(counterclockwise)

Figure 4 -1. Suction or Discharge Service Valve

4-1 T-312

4.3 INSTALLING MANIFOLD GAUGES

The manifold gauge set can be used to determine
system operating pressures, add charge, equalize or
evacuate t he system.

Low Pressure

Gauge

Opened
(Backseated )
Hand Valve

To Low Side
Access Valve

1

2

High Pressure

Gauge

Closed
(Frontseated)
Hand Valve

To High Side
Access Valve

3

BLUE

3

RED

3

YELLOW

4

5

(Red Knob)

6

(Blue Knob)

2

4

1. Manifold Gauge Set

2. Hose Fitting (0.5-16 Acme)

3. Refrigeration and/or Evacuation Hose
. (SAE J2196/R-134a)

4. Hose Fitting w/O-ring (M14 x 1.5)

5. High Side Field Service Coupler

6. Low Side Field Service Coupler

Figure 4-2. Manifold Gauge Set (R-134a)

4.3.1 Installing R-134a Manifold Gauge Set

An R-134a manifold gauge/hose set with self-sealing
hoses is required for service of models covered within
this manual. The manifold gauge/hose set is available
from Carrier Transicold. (CTD P/N 07-00294-00, which
includes items 1 through 6, see Figure 4-2.) To perform
service using the manifold gauge/hose set, do the
following:

a. Preparing Manifold Gauge/Hose Set For Use

1. If the manifold gauge/hose set is new or was
exposed to the atmosphere it will need to be
evacuated to remove contaminants and air as
follows:

2. Back seat (turn counterclockwise ) both field service
couplers (See Figure 4-2, items 5 and 6) and
midseat both hand valves.

3. Connect the yellow hose to a vacuum pump and an
R-134a cylinder.

4. Evacuate to 10 inches (0.69

BAR) of vacuum and
then charge with R-134a to a slightly positive
pressure of 1.0 psig (0.07 BAR).

5. Front seat both manifold gauge set hand valves and
disconnect from cylinder. The gauge set is now
ready for use.

b. Connecting Manifold Gauge/Hose Set

To connect the manifold gauge/hose set for reading
pressures, do the following:

1. Remove service valve stem cap and check to make
sure it is backseated. Remove access valve cap.

2. Connect the field service coupler (see Figure 4-2,
items 5 and 6) to the access valve.

3. Turn the field service coupling knob clockwise, which
will open the system to the gauge set.

4. Read system pressures.

5. Repeat the procedure to connect the other side of
the gauge set.

c. Removing the Manifold Gauge Set

1. While the compressor is still ON, backseat the high
side service valve.

2. Midseat both hand valves on the manifold gauge set
and allow the pressure in the manifold gauge set to
be drawn down to low side pressure. This returns
any liquid that may be in the high side hose to the
system.

CAUTION

To prevent trapping liquid refrigerant in
the manifold gauge set be sure set is
brought to suction pressure before
disconnecting.

3. Backseat the low side service valve. Backseat both
field service couplers and frontseat both manifold set
hand valves. Remove the couplers from the access
valves.

4. Install both service valve stem caps and access
valve caps (finger-tight only).

4.4 PUMPING THE SYSTEM DOWN OR

REMOVING THE REFRIGERANT CHARGE

NOTE

To avoid damage to the earth’s ozone layer ,
use a refrigerant recovery system whenever
removing refrigerant.

4.4.1 System Pumpdown

To service or replace the filter-drier, expansion valve,
evaporator coil, or suction line, pump the refrigerant into
condenser coil as follows:

a. Install manifold gauge set. (Refer to paragraph 4.3)

b. Start the unit and allow it to run in the cool mode for 15

to 20 minutes.

c. Unplug the suction pressure transducer(SPT).

NOTE

The following procedure may have to be
repeated several times to maintain the 0 to 2
psig (6.9 kPa) pressure depending upon
amount of refrigerant absorbed in the oil.

4-2T-312

d. Frontseat the liquid line (King) valve by turning

clockwise. Start system and run in cooling. Stop the
unit when the suction pressure reaches 1 psig (0.07
BAR).

e. Frontseat (close) suction service valve to trap the

refrigerant in the high side of the system between the
compressor suction service valve and the filter drier
inlet valve. The low side of the system will now be at 1
psig (0.07 BAR) pressure and ready for servicing,

f. Service or replace the necessary component on the

low side of the system.

g. Leak check connections. (Refer to paragraph 4.5)

h. Evacuate and dehydrate the low side. (Refer to

paragraph 4.6)

i. Reconnect the suction pressure transducer (SPT).

j. Clear the low pressure alarm. (Refer to paragraph

2.1.6)

4.4.2 Removing the Refrigerant Charge

Connect a refrigerant recovery system to the unit at the
condenser service (King) valve to remove refrigerant
charge. (See Figure 4-4) Refer to instructions provided
by the manufacturer of the refrigerant recovery system.

NOTE

1. Before opening up any part of the
system, a slight positive pressure should

be indicated on the gauge.

2. When opening up the refrigerant system,
certain parts may frost. Allow the part to
warm to ambient temperature before
dismantling; this avoids internal
condensation, which puts moisture into
the system.

3. When opening or closing the service
valves, care should be given to note if the
packing around the valve stem is worn or
may need adjustment to prevent
refrigerant leaks.

4.4.3 Refrigerant Removal From An Inoperative
Compressor.

To remove the refrigerant from a compressor that is not
operational, do the following:

a. Attach a manifold gauge set as shown in Figure 4-3

and isolate the compressor by front seating the
suction and discharge valves.

b. Recover refrigerant with a refrigerant reclaimer. If the

discharge service valve port is not accessible, it will
be necessary to recover refrigerant through the
suction service valve port only.

c. Service or replace components as required and leak

check the compressor.

d. Using refrigerant hoses designed for vacuum service,

connect a vacuum pump to center connection of
manifold gauge set. Evacuate compressor to 500
microns. Close off pump valve, isolate vacuum gauge
and stop pump. Wait 5 minutes to verify that vacuum
holds.

e. Once vacuum is maintained, recharge low side with

R-134a to 20 to 30 PSIG by admitting vapor from the
refrigerant cylinder. Backseat compressor service
valves and disconnect manifold gauge set.

3

DS

2

1

4

5

7

6

1. Discharge Service
Valve and Port

2. Suction Service
Valve and Port

3. Manifold Gauge

4. Vacuum Pump

5. Reclaimer

6. Refrigerant Cylinder

7. Thermistor Vacuum
Gauge

Set

Figure 4-3. Compressor Service Connections

4.4.4 Pump Down An Operable Compressor For
Repair

To service an operable compressor, pump the
refrigerant into the condenser coil as follows:

a. Install manifold gauge set. (See Figure 4-3)
b. Unplug the suction pressure transducer (SPT).
c. Frontseat the compressor suction service valve by

turning clockwise.

d. Start the unit and run in cooling until 10 ”/hg (0.69

BAR) of vacuum is reached. Shut the system down
and tag out system power source.

e. Frontseat the compressor discharge service valve

and wait 5 minutes to verify vacuum is maintained. If
the pressure rises above vacuum, open the
compressor discharge service valve and repeat steps
c and d until a vacuum is maintained.

f. Service or replace components as required and leak

check the compressor.

g. Using refrigerant hoses designed for vacuum service,

connect a vacuum pump to center connection of
manifold gauge set. Evacuate system to 500
microns. Close off pump valve, isolate vacuum gauge
and stop pump. Wait 5 minutes to verify that vacuum
holds.

h. Once vacuum is maintained, backseat compressor

service valves and disconnect manifold gauge set.
i. Reconnect the suction pressure transducer (SPT).
j. Clear the low pressure alarm. (Refer to paragraph

2.1.6)

4-3 T-312

4.5 REFRIGERANT LEAK CHECK

A refrigerant leak check should always be performed
after the system has been opened to replace or repair a
component.

To check for leaks in the refrigeration system, perform
the following procedure:

NOTE

It must be emphasized that only the correct
refrigerant drum should be connected to
pressurize the system. Any other gas or
vapor will contaminate the system, which will
require additional evacuation.

a. Ensure all the service valves and solenoid valves are

open. It will be necessary to energize the solenoid
valves from an external power source.

b. If the system is without refrigerant, charge the system

with refrigerant vapor to build up pressure between 30
to 50 psig (2.74to3.40BAR).

c. Add sufficient nitrogen to raise system pressure to a

maximum of 150 psig (10.21 BAR).

d. Check for leaks. It is recommended that an electronic

leak detector be used to find refrigerant leaks in a
system. Testing joints with soapsuds is satisfactory
and may be necessary under conditions when an
electronic leak detector will not function correctly.

e. Remove refrigerant from system and repair any

leaks.

f. Evacuate and dehydrate the system. (Refer to

paragraph 4.6)
g. Charge the unit. (Refer to paragraph 4.7)

h. Ensure that self-test has been performed and that

there are no errors or alarms indicated. (Refer to

paragraphs 2.1.5 and 2.1.6)

4.6 EVACUATION AND DEHYDRATION

4.6.1 General

The presence of moisture in a refrigeration system can
have many undesirable effects. The most common are
copper plating, acid sludge formation, “freezing-up” of
metering devices by free water, and formation of acids,
resulting in metal corrosion.

4.6.2 Preparation

NOTE

1. Using a compound gauge for
determination of vacuum level is not
recommended because of its inherent
inaccuracy.

2. Never evacuate an open drive
compressor below 500 microns.

a. Evacuate and dehydrate only after pressure leak test.

(Refer to paragraph 4.5)

b. Essential tools to properly evacuate and dehydrate

any system include a good vacuum pump with a
minimum of 6 cfm (10.2 m

3

/hr) volume displacement,

(CTD P/N 07-00176-11), and a good digital (micron)
vacuum indicator (CTD P/N 07--00414--00).

c. Keep the ambient temperature above 60_F (15.6_C)

to speed evaporation of moisture. If ambient
temperature is lower than 60_F (15.6_C), ice may
form before moisture removal is complete. It may be
necessary to use heater blankets, heat lamps or
alternate sources of heat to raise system
temperature.

4.6.3 Procedure for Evacuation and Dehydrating
System

a. Remove refrigerant using a refrigerant recovery

system. (CTD P/N MVS--115--F--L--CT for 115 volt
power source or CTD P/N MVS--240--F--L--CT for 240
volt power source)

b. The recommended method is connecting two lines

(3/8” OD copper tubing or refrigerant hoses designed
for vacuum service) to the manifold guage set. Attach
one line to the condenser service (King) valve and the
other line to the evaporator service port. (See
Figure 4-4)

c. Connect lines to unit and manifold and make sure

vacuum gauge valve is closed and vacuum pump
valve is open.

d. To speed up evacuation time, open solenoid valves

electrically. An additional vacuum pump may be
added and connected to the compressor suction
service port. (See Figure 4-4)

e. Start vacuum pump. Slowly open valves halfway and

then open vacuum gauge valve.

f. Evacuate unit until vacuum gauge indicates 1500

microns vacuum. Close gauge valve, vacuum pump
valve, and stop vacuum pump.

g. Break the vacuum with clean dry refrigerant or dry

nitrogen. Use the refrigerant that the unit calls for.
Raise system pressure to approximately 2 psig (0.14
BAR).

h. Remove refrigerant using a refrigerant recovery

system, or if using nitrogen vent to atmosphere.

i. Start vacuum pump and open all valves. Evacuate

unit to 500 microns vacuum.

j. Close off pump valve, isolate vacuum gauge in

system and stop pump. Wait five minutes to see if
vacuum holds.

k. With a vacuum still in the unit, the refrigerant charge

may be drawn into the system from a refrigerant
container on weight scales. (Refer to paragraph 4.7)

4-4T-312

1. Reclaimer

DS

2

4

2. Manifold Guage Set

3. Thermistor Vacuum Guage

4. V acuum Pump

5. Refrigerant Cylinder

6. Evaporator Service Port

3

1

7. Liquid Line (King) Valve
and Service Port

8. Discharge Service Port

5

Discharge

DRIVER SOLENOID
VALVE

Liquid
Suction

MAIN LIQUID LINE
SOLENOID VALVE

CONDENSER
ASSEMBLY

CONDENSER

SUBCOOLER

DISCHARGE LINE
SERVICE VALVE

PARCEL RACK
LIQUID LINE
SOLENOID VALVE

FILTER

DRIER

SIGHT-­GLASS

FUSIBLE
PLUG

DISCHARGE LINE

TXV

DRIVER EVAPORATOR
ASSEMBLY

TXV

PASSENGER EVAPORATOR ASSEMBLY

PARCEL EVAPORATOR
ASSEMBLY

TXV

TXV

7

DISCHARGE
CHECK VALVE

PARCEL EVAPORATOR

ASSEMBLY

TXV BULB

SERVICE PORT

TXV BULB

6

SERVICE
PORT

SERVICE
PORT

SUCTION LINE

SERVICE PORT

8

COMPRESSOR

Figure 4 -4. Refrigerant Service Connections

4-5 T-312

OPTIONAL VACUUM PUMP

4.7 ADDING REFRIGERANT TO SYSTEM

4.7.1 Checking Refrigerant Charge

a. Connect an accurate high pressure gauge to the

discharge service port at the compressor. (See
Figure 4-4)

b. The condenser coil should be clean and free of any

debris.

c. Coach engine operating at high idle (800--1000RPM).

d. The compressor should be fully loaded (six cylinder

operation).

e. Unit must be operating in the cool mode until the

discharge pressure has stabilized (3 to 5 minutes)
and the interior temperature is between 70 and 80_F
(21.1 and 26.7_C).

f. Discharge pressure at least 150 psig (10.21 BAR)

and stable for R-134a systems (It may be necessary
to partially block condenser airflow to raise discharge
pressure).

g. Observe the Liquid Line Sight Glass and use the

following chart to determine the condition of the
refrigerant charge:

Table 4-1. Checking Refrigerant Charge

Sight Glass

Observation

Liquid present

Clear of all bubbles

charge -- Continue to step

Condition

Good/Possible over

i.

Liquid present

Occasional bubbles

Good

present

Liquid present

Many bubbles present

Possible under charge --

Continue to step i.

h. If the conditions in steps b. thru f. are met and there is

still doubt about the refrigerant charge level use
Table 4-2:

Table 4-2. Checking Refrigerant Charge

Condenser Inlet Air

Temperature

Discharge Pressure

Range

____F ____C PSIG BAR

60 16 110--135 7.48--9.19
65 18 120--145 8.16--9.87
70 21 130--155 8.85--10.55
75 24 140--165 9.53--11.23
80 27 150--175 10.21--11.91
85 29 160--186 10.89--12.66
90 32 175--200 11.91--13.61
95 35 190--212 12.93--14.42

i. With an accurate temperature gauge, measure the

condenser inlet air temperature.

NOTE

Do not use a temperature gun as it measures
surface temperature and not air temperature.

1. If the actual discharge pressure is higher than the
discharge pressure range, the system may be over
charged.

2. If the actual discharge pressure is lower than the
discharge pressure range, the system may be under
charged.

3. If the actual discharge pressure is in the discharge
pressure range, the system charge is adequate.

NOTE

Many system related problems will effect
system pressures. Use Table 3-5 General
System Troubleshooting Procedures to
determine other possible causes before
adding or removing refrigerant.

4.7.2 Adding Full Charge

a. Evacuate and dehydrate system. (Refer to paragraph

4.6.)

b. Place appropriate refrigerant cylinder on scales and

connect charging hose from container to filter-drier

inlet valve. Remove air from hoses.
c. Note weight of refrigerant and container.
d. Open liquid valve on refrigerant container. Midseat

filter-drier inlet valve and allow refrigerant to flow into

the unit. Refer to paragraph 1.3 for correct charge.
e. When drum weight (scale) indicates that the correct

charge has been added, close liquid line valve on

drum and backseat the filter-drier inlet valve.

4.7.3 Adding Partial Charge

NOTE

Refrigerant charge is critical, when adding
charge to the unit do not add any more
charge to the system after bubbles have
been eliminated from the sight glass.

a. Start the vehicle engine and allow the system to

stabilize. (Refer to 4.7.1a. to f.)
b. Connect charging hose from appropriate refrigerant

cylinder vapor valve to compressor suction service

valve.
c. Open cylinder valve and add vapor charge. Under the

above conditions, the system is properly charged

when the condenser sight glass is clear with

occasional bubbles showing. Add or remove

refrigerant until the proper charge is obtained.
d. Backseat suction service valve. Close vapor valve on

refrigerant drum. Replace all valve caps.

4.8 CHECKING FOR NONCONDENSIBLES

To check for noncondensibles, proceed as follows:
a. Stabilize system to equalize pressure between the

suction and discharge side of the system. The engine

needs to be off for several hours.
b. Measure temperature at any of the copper tubing in

the condenser.
c. Check pressure at the compressor discharge service

valve.
d. Determine saturation pressure as it corresponds to

the condenser temperature using the

Temperature-Pressure Chart, Table 4-6.

4-6T-312

e. If gauge reading is 3 psig (.2 BAR) or higher than the

calculated P/T pressure in step d, noncondensibles
are present.

f. Remove refrigerant using a refrigerant recovery

system. (Refer to paragraph 4.6.3)

g. Evacuate and dehydrate the system. (Refer to

paragraph 4.6)

h. Charge the unit. (Refer to paragraph 4.7)

4.9 CHECKING AND REPLACING HIGH
PRESSURE CUTOUT SWITCH

4.9.1 Replacing High Pressure Switch

a. The high pressure switch is equipped with schrader

valve to allow removal and installation without
pumping the unit down.

b. Unplug the wiring from the switch.

c. Check switch operation. (Refer to paragraph 4.9.2)

d. Replace switch if it does not function as outlined

below. (Refer to paragraph 4.9.2)

4.9.2 Checking High Pressure Switch

WARNING
DO NOT USE A NITROGEN CYLINDER
WITHOUT A PRESSURE REGULATOR

DO NOT USE OXYGEN IN OR NEAR A
REFRIGERATION SYSTEM AS AN
EXPLOSION MAY OCCUR.

f. Close cylinder valve and release pressure through

the bleed-off valve. As pressure drops to cut-in point,
the switch contacts should close, indicating continuity
on the ohmmeter.

4.10 FIL TER-DRIER

4.10.1.To Check Filter Drier

Check for a restricted or plugged filter-drier by feeling
the liquid line inlet and outlet connections of the
filter-drier. If the outlet side feels cooler than the inlet
side, then the filter-drier should be changed.

4.10.2.To Replace Filter Drier

a. Pump down the unit. (Refer to paragraph 4.4)
b. Replace filter-drier, ensuring that the arrow points in

the direction of the refrigerant flow .

c. Drier can be evacuated at liquid line service valve.

(See Figure 4-4)

d. Check refrigerant charge. (Refer to paragraph 4.7.1)

2

1

3

4

8

5

6

a. Remove switch from unit. All units are equipped with

schrader valves at the high pressure switch
connection.

b. Connect an ohmmeter across switch terminals. If the

switch is good, the ohmmeter will indicate continuity,
indicating that the contacts are closed.

1

4

1. Cylinder Valve

2

5

and Gauge

2. Pressure Regulator

3. Nitrogen Cylinder

4. Pressure Gauge,

3

6

0 to 400 psig

(0 to 2.8 mPa)

5. Bleed-Off Valve

6. 1/4 inch Connection

Figure 4-5. Checking High Pressure Switch

c. Connect switch to a cylinder of dry nitrogen. (See

Figure 4-5)

d. Set nitrogen pressure regulator higher than cutout

point on switch being tested. (Refer to paragraph 1.3)

e. Open cylinder valve. Slowly open the regulator valve

to increase the pressure until it reaches cutout point.
The switch should open, which is indicated by an
infinity reading on an ohmmeter (no continuity).

7

1. Power Head Assembly

2. Equalizer Connection

3. Bulb

4. Cage Assembly

5. Seat Gasket

6. Body Flange

7. Capscrew

8. Body Flange Gasket

Figure 4 -6. Thermostatic Expansion Valve

4.11 THERMOSTATIC EXPANSION VALVE

The thermostatic expansion valve (TXV) is an
automatic device which maintains constant superheat
of the refrigerant gas leaving the evaporator regardless
of suction pressure. The valve functions are: (a)
automatic response of refrigerant flow to match the
evaporator load and (b) prevention of liquid refrigerant
returning to the compressor. Unless the valve is
defective, it seldom requires any maintenance. All
TXV’s are non--adjustable.

4.11.1 Replacing the Expansion Valve (See
Figure 4 -6)

a. Pump down low side of the unit. (Refer to paragraph

4.4)

b. Remove insulation (Presstite) from expansion valve

bulb.

4-7 T-312

c. Loosen retaining straps holding bulb to suction line

and detach bulb from the suction line.

d. Loosen flare nut on equalizer line and disconnect

equalizer line from the expansion valve.

e. Remove capscrews and lift off power head and cage

assemblies and gaskets.

f. Check, clean and remove any foreign material from

the valve body, valve seat and mating surfaces.

NOTE

Do not adjust the new replacement expansion
valve. Valves are preset at the factory.

g. Using new gaskets, install new cage and power head

assemblies provided with repair kit.

h. The thermal bulb is installed below the center of the

suction line (four or eight o’clock position). This area
must be clean to ensure positive bulb contact. Strap
thermal bulb to suction line and insulate both with
“Presstite.” Ensure that retaining straps are tight.
(See Figure 4-7)

i. Connect equalizer line to the expansion valve.

j. Evacuate and dehydrate. (Refer to paragraph 4.6)

k. Open filter-drier inlet valve (liquid line service valve)

and all service valves.

l. Run the coach for approximately 30 minutes on fast

idle.

m.Check refrigerant charge. (Refer to paragraph 4.7.1)

n. Check superheat. (Refer to paragraph 4.11.2)

d. Place temperature thermocouple in contact with the

suction tube and parallel to the TXV bulb, and then
secure loosened clamp making sure both bulbs are
firmly secured to suction line. (See Figure 4-7)
Reinstall insulation around the bulb.

e. Connect an accurate low pressure gauge (or install a

manifold gauge set) to the service port on the leaving
side of the evaporator. (Refer to paragraph 4.3)

f. Close evaporator access door being careful to route

thermocouple sensing wire and guage hose thru the
access hole to outside the evaporator.

g. Start coach and run on fast idle until unit has

stabilized, about 20 to 30 minutes.

h. From the temperature/pressure chart, determine the

saturation temperature corresponding to the
evaporator outlet pressure. (Refer to Table 4-6)

i. Note the temperature of the suction gas at the

expansion valve bulb. Subtract the saturation
temperature determined in step 8 from the
temperature measured in this step. The difference is
the superheat of the suction gas.

j. Repeat steps 8. and 9. six times at three minute

intervals and average the six readings to determine
average superheat. Average superheat should be 12
to 18_F (6.7 to 10.1_C).

4.12 MODEL 05G COMPRESSOR MAINTENANCE

3

2

4

5

1

1. Suction Line (end view)

2. TXV Bulb Clamp

3. Nut and Bolt (clamp)

4. Thermocouple

5. TXV Bulb (Shown in the
four o’clock position)

Figure 4 -7. Thermostatic Expansion Valve

Bulb and Thermocouple Installation

4.11.2 To Check/Measure Superheat

NOTE

All readings must be taken from the leaving side
of the evaporator.

a. Open filter access door.

b. Remove Presstite insulation from expansion valve

bulb and suction line.

c. Loosen one TXV bulb clamp and make sure area

under clamp (above TXV bulb) is clean.

4.12.1 Removing the Compressor

If compressor is inoperative and the unit still has
refrigerant pressure, isolate the compressor and
remove the refrigerant. (Refer to paragraph 4.4.3)

If compressor is operative, perform a pump down.
(Refer to paragraph 4.4.4)

a. Turn main battery disconnect switch to OFF position

and lock.

b. Loosen the compressor drive belt, and remove.

c. Loosen bolts at suction and discharge service valve

flanges and break seal to be sure pressure is
released.

d. Remove bolts from suction and discharge service

valve flanges.

e. Tag and disconnect wiring to the high pressure cutout

switch, discharge pressure transducer, suction
pressure transducer, unloaders and the clutch.

f. Remove four bolts holding compressor to base.

g. Attach sling or other device to the compressor and

remove compressor from the coach through the right
rear access door.

h. Set the compressor on a sturdy work surface.

4-8T-312

4.12.2 Re--installing the Compressor

NOTES

1. The service replacement 05G
compressors are sold without shutoff
valves. Valve pads are installed in their
place. The optional unloaders are not
supplied, as the cylinder heads are shipped
with plugs. The customer should retain the
original unloader valves for use on the
replacement compressor.

2. Thepistonplugthatisremovedfromthe
replacement compressor head must be
installed in the failed compressor if
returning for warranty.

3. Do not interchange allen head capscrews
that mount the piston plug and unloader;
they are not interchangeable.

4. Check oil level in service replacement
compressor. (Refer to paragraphs 1.3 and

4.12.4)

d. Re--install and tension the compressor drive belt.
e. Unlock and turn main battery disconnect switch to ON

position..

f. Attach two lines (with hand valves near vacuum

pump) to the suction and discharge service valves.

g. Fully backseat (open counterclockwise) both suction

and discharge service valves.

h. Remove vacuum pump lines and install manifold

gauges.

i. Start unit and check refrigerant level. (Refer to

paragraph 4.7.1)

j. Check compressor oil level. (Refer to paragraph

4.12.4) Add or remove oil if necessary.

k. Check compressor unloader operation.

4.12.3 Compressor Unloaders

Although the electric unloaders are non--adjustable,
they will require some periodic maintenance. Service
kits are available for repair of the electric unloaders
solenoid and stem assemblies.

To check the unloaders proceed as follows:.

a. Ensure that the compressor is fully loaded. Heat the

interior of the coach if necessary.

5. Service replacement compressors are
supplied with a suction filter sock for initial
startup. Ensure the filter sock is installed
and removed in accordance with the
instructions furnished.

a. Remove the three socket head capscrews from both

unloader valves on the side heads of the 05G
compressor. Remove the unloader valve and bypass
piston assembly , keeping the same capscrews with
the assembly. (See Figure 4-8) The original unloader
valve must be transferred to the replacement
compressor. The plug arrangement removed from
the replacement is installed in the original
compressor as a seal. If piston is stuck, it may be
extracted by threading a socket head capscrew into
top of piston. A small T eflon seat ring at the bottom of
the piston must be removed.

COMPRESSOR

HEAD

GASKET

BYPASS

PISTON

PLUG

SPRING

FLANGE

COVER

CAPSCREWS

(NOT INTERCHANGEABLE WITH

CONTROL VALVE SCREWS)

Figure 4 -8. Removing Bypass Piston Plug

b. Remove the high pressure switch and pressure

transducer assemblies and install on replacement
compressor after checking switch operation.

c. Install compressor in unit by performing steps c.

through g. in reverse sequence. It is recommended
that new locknuts be used when replacing
compressor. Install new gaskets on service valves
and tighten bolts uniformly.

12

1

2

11

10

9

3

4

5

8

6

7

1. Electric Unloader
Val ve

2. Suction Service
Valve Charging Port

3. Suction Service
Val ve

4. Clutch

5. Oil Fill Plug

7. Oil Drain Plug

8. Oil Level Sight
Glass

9. Oil Pump

10. O’Ring
1 1. Discharge Service

Val ve

12. Service Port

6. Bottom Plate

Figure 4-9. Model O5G Compressor

b. Connect manifold guages to the compressor.
c. Slowly frontseat the suction valve until 26 psig shows

on the suction guage. The first unloader should
energize (check for magnetism at the unloader coil)
increasing suction pressure by 3 to 5 psig.

d. Slowly open the suction valve until the suction gauge

reads 32 psig. The first unloader should de--energize
decreasing suction pressure by 3 to 5 psig to show it
is operating properly.

e. To check the second unloader, continue to frontseat

the suction valve until 21 psig shows on the suction

4-9 T-312

guage. The second unloader should energize (check
for magnetism at the unloader coil) increasing suction
pressure by 3 to 5 psig.

f. Slowly open the suction valve until the suction guage

reads 28 psig. The first unloader should de--energize
decreasing suction pressure by 3 to 5 psig to show it
is operating properly.

g. Back seat the suction service valve, remove the

guage(s) to resume normal operation.

4.12.4 Compressor Oil Level

NOTE

The compressor should be fully loaded (six
cylinder operation); the unit should be fully
charged and the compressor crankcase
should be warm to the touch.

a. Start the unit and allow the system to stabilize.

b. Check the oil sight glass on the compressor to ensure

that no foaming of oil is present after 20 minutes of
operation. If oil is foaming excessively after 20
minutes of operation, check the refrigerant system for
flood-back of liquid refrigerant. Correct this situation
before proceeding.

c. Check the level of oil in oil level sight glass

immediately after shutting down the compressor. The
lowest level visible should be at the bottom of the
sightglass and the highest level should be at the
middle of the sight glass. (See Figure 4-9)

4.12.5 Adding Oil with Compressor in System

Two methods for adding oil are: the oil pump method
and closed system method.

NOTE

Special care must be taken when working
with POE oil that is used with HFC
refrigerants such as R--134a, as POE oil is
very hygroscopic. (POE oil will easily absorb
water.) Do not leave POE oil containers
open to the atmosphere.

4.12.5.1. Oil Pump Method

a. One compressor oil pump that may be purchased is a

Robinair part no. 14388. This oil pump adapts to one
U.S. gallon (3.785 liters) metal refrigeration oil
container and pumps 2-1/2 ounces (72.5 milliliters)
per stroke when connected to the suction service
valve port. Also, there is no need to remove pump
from can after each use.

b. When the compressor is in operation, the pump

check valve prevents the loss of refrigerant while
allowing servicemen to develop sufficient pressure to
overcome the operating suction pressure to add oil,
as necessary.

c. Backseat suction service valve and connect oil

charging hose to port. Crack open the service valve
and remove air from the oil hose at the oil pump. Add
oil as necessary.

NOTE

Allow time (at least 60 seconds) for the oil
to flow thru to the crankcase and show on
the sightglass.

4.12.5.2. Closed System Method

a. Install manifold gauge set. (See Figure 4-3)
b. Unplug the suction pressure transducer (SPT).
c. Frontseat the compressor suction service valve by

turning clockwise.

d. Start the unit and run in cooling until 10 ”/hg (25.4

cm/hg) of vacuum is reached. Shut the system down
and tag out system power source.

e. Frontseat the compressor discharge service valve

and wait 5 minutes to verify vacuum is maintained.

f. Remove the crankcase oil fill plug on the side of the

crankcase.

g. Replace the crankcase oil fill plug with a Carrier

Service Parts no. OTBO889 fitting. This fitting has a
1/4 inch flare access port with a shrader valve.

h. Using refrigerant hoses designed for vacuum service,

connect a vacuum pump to center connection of
manifold gauge set.

CAUTION
Care Must Be Taken To Ensure That The
Manifold Common Connection Remains
Immersed In Oil At All Times Or Air And
Moisture Will Be Drawn Into The System.

i. Connect a refrigerant hose with a shrader depressor

to the fitting described in step g. above, put the other
end of the hose in a fresh oil container.

j. Evacuate the compressor and observe the oil level in

the compressor crankcase. When the desired oil

level is reached, disconnect the hose from the fitting.
k. Reinstall the crankcase oil fill plug.
l. Using refrigerant hoses designed for vacuum service,

connect a vacuum pump to center connection of

manifold gauge set. Evacuate system to 500

microns. Close off pump valve, isolate vacuum gauge

and stop pump. Wait 5 minutes to verify that vacuum

holds.
m.Once vacuum is maintained, backseat compressor

service valves and disconnect manifold gauge set.
n. Reconnect the suction pressure transducer(SPT).

4.12.6 Adding Oil to Service Replacement

Compressor

Service replacement compressors may or may not be
shipped with oil.

If the replacement compressor is shipped without oil,
add oil through the oil fill plug. (See Figure 4-9)

4.12.7 Removing Oil from the Compressor:

a. If the lowest oil level observed in paragraph 4.12.4,

step c., is above middle of the sight glass on

compressor crankcase, oil must be removed from the

compressor by performing the following procedure. If

lowest oil level visible is below bottom of the

sightglass, oil must be added to the compressor by

following the procedure in paragraph 4.12.5.

4-10T-312

b. Close (frontseat) suction service valve and pump unit

Resi

O

h

downto3to5psig(21to34kPa).Reclaim remaining
refrigerant.

NOTE

If oil drain plug is not accessible, it will be
necessary to extract oil through the oil fill plug
with a siphon tube.

WARNING

EXTREME CARE MUST BE TAKEN TO
ENSURE THAT ALL THE REFRIGERANT
HAS BEEN REMOVED FROM THE
COMPRESSOR CRANKCASE OR THE
RESULTANT PRESSURE WILL FORCIBLY
DISCHARGE COMPRESSOR OIL.

c. Remove the oil drain plug on the bottom plate of the

compressor and drain the proper amount of oil from
the compressor. Replace the plug securely back into
the compressor.

d. Repeat step a. to ensure proper oil level.

Table 4 -3. Temperature Sensor

(AT, TSC, TSD and TSR) Resistance

Temperature

_F _C

stanceIn

ms

-- 2 0 --28.9 165,300

-- 1 0 --23.3 117,800

0

10 --12.2

--17.8 85,500

62,400
20 -- 6 . 7 46,300
30 -- 1 . 1 34,500
32

0

32,700

40 4.4 26,200
50 10.0 19,900
60 15.6 15,300
70 21.1 11,900
77 25 10,000
80 26.7 9,300
90 32.2 7,300

100 37.8 5,800
110 43.3 4,700
120 48.9 3,800

NOTE

This system is equipped with three
temperature sensors, two located in the
return air ducts inside the coach, the third
sensor is located in the condenser section.
The two inside sensors are wired in parallel
and together send an averaged signal to the
controller. If one of these sensors fails the
control function will continue with the
remaining sensor. The sensor located in the
condenser section reads outdoor
temperature.

4.14 HUMIDITY SENSOR CHECKOUT

a. Use a sling psychrometer or similar device to check

relative humidity inside the coach.

NOTE

System can be shut down but 5 vdc power
must be applied to the humidity sensor to
enable checking.

b. Measure voltage across the sensor and compare to

values in Table 4-4 for the measured relative
humidity. A reading within two percent of the values in
the table would be considered good.

c. At least one sensor lead must be disconnected from

the controller before any reading can be taken. Not
doing so will result in a false reading. Two preferred
methods of determining the actual test temperature
at the sensor are an ice bath at 32_F (0_C) and/or a
calibrated digital temperature meter.

d. If the driver display indicates that temperature at

sensor is --40_F (--40_C), sensor could be open. If
driver display indicates that temperature at sensor is
127_F (52.8_C), sensor could be shorted.

Table 4 -4. Humidity Sensor (HS) Voltage

%RH Volt age %RH Vol tage %RH Vo ltag e

30 0.990 55 1.815 80 2.640
35 1.155 60 1.980 85 2.805
40 1.320 65 2.145 90 2.970
45 1.485 70 2.310 95 3.168
50 1.650 75 2.475

4.15 SUCTION AND DISCHARGE PRESSURE
TRANSDUCER CHECKOUT

4.13 TEMPERA TURE SENSOR CHECKOUT

a. An accurate ohmmeter must be used to check

resistance values shown in Table 4-3.

b. Due to variations and inaccuracies in ohmmeters,

thermometers or other test equipment, a reading
within two percent of the chart value would be
considered good. If a sensor is bad, the resistance
value would usually be much higher or lower than the
value given in the Table 4-3.

NOTE

1. System must be operating to check
transducers.

2. Both transducers are mounted on the
compressor

a. With the system running, use the driver display or

manifold gauges to check suction and/or discharge
pressure(s).

4-11 T-312

b. Use a digital volt-ohmmeter to measure voltage

across the transducer and compare to values in
Table 4-5. A reading within two percent of the values
in the table would be considered good.

Table 4-5. Suction and Discharge Pressure

Transducer (SPT and DPT) Voltage

Psig Vo l tag e Psig Volt age Psig Voltage

20” 0.369 105 1.495 220 2.622
10” 0.417 110 1.544 225 2.671

0 0.466 115 1.593 230 2.720

5 0.515 120 1.642 235 2.769
10 0.564 125 1.691 240 2.818
15 0.614 130 1.740 245 2.867

20

0.663 135 1.789 250 2.916

25 0.712 140 1.838 255 2.965
30 0.761 145 1.887 260 3.014
35 0.810 150 1.936 265 3.063
40 0.858 155 1.985 270 3.112
45 0.907 160 2.034 275 3.161
50 0.956 165 2.083 280 3.210
55 1.007 170 2.132 285 3.259
60 1.054 175 2.181 290 3.308
65 1.103 180 2.230 295 3.357
70 1.152 185 2.279 300 3.406
75 1.204 190 2.328 305 3.455
80 1.250 195 2.377 310 3.504
85 1.299 200 2.426 315 3.553
90 1.348 205 2.475 320 3.602
95 1.397 210 2.524 325 3.651

100 1.446 215 2.573 330 3.700

d. Remove blower transitions ducts.
e. Remove the four bolts securing the evaporator motor

mounting plate, motor and blower housing assembly
to the bottom panel.

f. Remove motor and blower wheel assembly by sliding

out of evaporator housing.

g. Repair or replace any defective component(s), as

required.

h. Replace by reversing steps b. thru f.

4.18 ACCESSING MAIN EVAPORATOR MOTOR
BRUSHES

a. Turn main battery disconnect switch to OFF position

and lock.
b. Remove access door. (Refer to 4.17.b.)

c. Disconnect electrical connections to the motor.
d. With a marker, trace the outline of the motor on the

motor plate.
e. Remove the four brush access doors on the motor.

f. Service two brushes (top front and top rear).
g. Remove the four bolts securing the evaporator motor

to the mounting plate.
h. Rotate the motor to gain access to the lower front

brush.
i. Rotate the motor the opposite way to gain access to

the lower rear brush.
j. Rotate the motor back to its feet and position back to

its original position guided by the outline drawn in step

d.
k. Re--secure the motor with the four bolts removed in

step g. Check fan rotation, insuring that the fan

wheels do not make contact with the fan housings.

l. Complete the procedure by performing steps a. thru

c. in reverse.

4.16 REPLACING SENSORS AND
TRANSDUCERS

a. Turn main battery disconnect switch to OFF position

and lock.

b. Tag and disconnect wiring from defective sensor or

transducer.

c. Remove and replace defective sensor or transducer .

d. Connect wiring to replacement sensor or transducer.

e. Checkout replacement sensor or transducer. (Refer

to paragraph 4.13, 4.15 or 4.14, as applicable.)

4.17 SERVICING MAIN EVAPORATOR BLOWER
ASSEMBLY

a. Turn main battery disconnect switch to OFF position

and lock.

b. Remove access door located in the #3 baggage

compartment. To remove the access door, unlatch,
then open the door enough to slide the hinge pins out
of the pin brackets.

c. Disconnect electrical connections to the motor.

4.19 SERVICING MOTOR BRUSHES

If the brushes are broken, cracked, severely chipped, or
worn to 1/3 their original length, replace them.

a. Remove the four brush access doors on the motor.

b. With fingers or a suitable hook, lift the brush spring

end up so the brush may slide up and out of the
holder. Loosen the brush screw to remove the brush
shunt terminal. Remove the brush.

c. T o replace, lift the brush spring and place the brush in

the holder. Position the end of the spring on top of the
brush.

d. Connect the brush shunt terminal to its proper

crossover with the brush screw assembled loosely.

NOTE

Assure positioning of the brush to permit the
brush shunt to travel freely in the holder slot
as the brush wears. If the brush hangs up,
commutator damage and motor failure will
result

e. Tighten screw.

4-12T-312

4.20 SERVICING THE MAIN EVAPORA T OR AND
HEATER COIL

j. Remove condenser module by sliding out on

mounting rails.

a. Drain engine coolant from the heater coil.

b. Pump down low side of the HVAC system. (Refer to

paragraph 4.4.1.)

c. Remove remaining refrigerant. (Refer to paragraph

4.4.)

d. Remove the evaporator motor by following paragraph

4.17 steps a. thru f.

e. Disconnect all remaining electrical connections,

move wires out of the way.

f. Remove the evaporator electrical panel assembly.

g. Remove the liquid line (3 connection points) and the

discharge line (2 connection points) that pass thru the
evaporator and connect to the evaporator.

h. Disconnect and remove the suction line.

i. Disconnect and remove the heater hoses.

j. Remove the door frame surrounding the evaporator

enclosure.

k. Remove the four bolts that secure the coil bracket to

the drain pan. Leave the coil bracket bolted to the
evaporator coil until the coil has been removed from
the coach.

WARNING

WHEN MOVING THE COIL CARE MUST
BE TAKEN TO AVOID PERSONAL INJUR Y
BECAUSE OF THE WEIGHT OF THE COIL.

l. Brace the top of the coil hold it in position.

m.Remove the four bolts that secure the top of the coil to

the evaporator housing.

n. Rotate the top of the coil till the coil is horizontal and

slide out of the evaporator housing.

o. Re-install by performing the above procedure in

reverse.

4.21 REMOVING THE CONDENSER ASSEMBLY

4.22 SERVICING THE CONDENSER COIL

a. Remove the condenser assembly from the coach.

(Refer to paragraph 4.21)
b. Remove side panel (with control box).
c. Remove front shroud and panel assemblies.
d. Unbraze coil/tubing connections and roll front module

assembly forward to provide clearance for coil

removal.
e. Remove condenser coil.
f. Repair or replace the condenser coil.
g. Re-install by performing the above procedure in

reverse.

4.23 SERVICING THE CONDENSER MOTOR

a. Turn main battery disconnect switch to OFF position

and lock.
b. Remove appropriate front condenser grill.
c. Remove fan blade, secure the shaft key to the motor

shaft or fan hub slot.
d. Disconnect the wires to the motor.
e. Remove the four motor base mounting screws.
f. Remove the motor and place on workbench.
g. Repair or replace defective component(s), as

required.
h. For brush inspection/replacement refer to paragraph

4.19.

i. Re-install by performing the above procedure in

reverse.

4.24 SERVICING THE DRIVER CONTROL BOX

The driver control box is located behind the return air
panel below the passenger side dash and under the
right headlight. (See Figure 4-10.) Remove the return
air panel by removing the eight screws holding the panel
in place. Remove and service the control box by
performing the following procedure:

a. Remove two side access panels from rear of the last

baggage bay.

b. Remove and reclaim the entire refrigerant charge.

(Refer to paragraph 4.4.2.)

c. Turn main battery disconnect switch to OFF position

and lock.

d. Disconnect all electrical leads to the module.

e. Disconnect refrigerant lines to the module.

f. Remove the door latch stud to the right side of the

condenser compartment.

g. Remove the front panel and the eight screws

fastening the condenser to the coach.

h. Remove the stabilizing bracket on the top of the

condenser.

i. Remove the eight screws securing the condenser

door hinges to the frame.

HEADLIGHT
DRIVER
CONTROL
BOX

Figure 4 -10. Removing Driver Control Box

a. Turn main battery disconnect switch to OFF position

and lock.

4-13 T-312

b. Remove the power wire from the power stud and the

connector from the box.

c. Remove the 1/4-inch capscrew at the upper right

cover of the box. Pull the box laterally approximately
3/4-inch to the right to remove it from the pocket.

d. Rotate box counterclockwise 90 degrees as shown in

Figure 4-10 and carefully lift the box out.

e. Repair or replace defective components, as

necessary.

f. Re-install the driver control box by reversing the

above procedure.

4.25 SERVICING THE DRIVER EVAPORATOR

4.25.1 Access Cover Removal

a. Remove stepwell access cover and disconnect

2-inch flex hose adapter.

b. Using a flat screwdriver, unfasten three 1/4 turn

fasteners from access cover on driver evaporator
assembly.

c. Open driver storage compartment and remove plug in

sheet metal.

d. With screwdriver, unfasten the last 1/4 turn fastener.

e. Draw access cover towards the rear and slide to the

right.

4.25.2Blower Removal

a. Disconnect plugs and speed control from the blower.

b. Undo latch and push the blower towards the rear.

c. Drop the blower down and remove.

4.25.3 Air filter Removal

a. With the access cover removed, slide right hand side

air filter towards center and turn right corner past
edge.

b. Slide left hand side filter to the right and repeat as

above.

c. Clean/replace filter and re-install.

4.25.4 Removal of Evaporator/Heater Coil
Assembly

a. Clamp off silicon hose close to the input and output

end of the heater core.

b. Disconnect hose clamps and separate hose from

fitting.

c. Pump down the refrigerant system. (Refer to

paragraph 4.4.1)

d. Disconnect liquid line solenoid valve plug.
e. Disconnect expansion valve thermal bulb attached to

the 7/8-inch copper tube.
f. Disconnect 7/8 and 3/8-inch copper lines.

g. Remove screws that attach the heater core to the

unit.

h. Lift evaporator coil up and pull towards the rear for

removal.

4.25.5 RAM Air Actuator Removal

a. Disconnect the plug.

b. Remove the no. 10 screw from the end of the spring

on the RAM air actuator.

4.26 SERVICING THE PARCEL RACK

EVAPORATOR

4.26.1 Motor Removal

a. Disconnect the motor wires from the connector.

b. Remove the two bolts from the motor mount and

remove the motor.

c. Remove the blower and motor assembly.

4.26.2 Removal of Parcel Rack Evaporator Coil

a. Pump down the refrigerant system. (Refer to

paragraph 4.4.1)

b. Remove the side access panel.
c. Disconnect expansion valve thermal bulb attached to

the 7/8-inch copper tube.
d. Disconnect 7/8 and 3/8-inch copper lines.

e. Lift evaporator coil up and push towards the rear for

removal.

4-14T-312

Table 4-6. R-134a Temperature - Pressure Chart

Temperature

F C

-- 4 0 -- 4 0 14.6 37.08 0.49

.35 .37 12.3 31.25 0.42

-- 3 0 -- 3 4 9.7 24.64 0.33

-- 2 5 -- 3 2 6.7 17.00 0.23

-- 2 0 -- 2 9 3.5 8.89 0.12

-- 1 8 -- 2 8 2.1 5.33 0.07

-- 1 6 -- 2 7 0.6 1.52 0.02

Temperature Pressure

F C

-- 1 4 -- 2 6 0.4 0.03 0.03

-- 1 2 -- 2 4 1.2 0.08 0.08

-- 1 0 -- 2 3 2.0 0.14 0.14

-- 8 -- 2 2 2.9 0.20 0.20

-- 6 -- 2 1 3.7 0.26 0.26

-- 4 -- 2 0 4.6 0.32 0.32

-- 2 -- 1 9 5.6 0.39 0.39

0 -- 1 8 6.5 0.46 0.45

2 -- 1 7 7.6 0.53 0.52

4 -- 1 6 8.6 0.60 0.59

6 -- 1 4 9.7 0.68 0.67

8 -- 1 3 10.8 0.76 0.74

10 -- 1 2 12.0 0.84 0.83

12 -- 11 13.2 0.93 0.91

14 -- 1 0 14.5 1.02 1.00

16 -- 9 15.8 1.11 1.09

18 -- 8 17.1 1.20 1.18

20 -- 7 18.5 1.30 1.28

22 -- 6 19.9 1.40 1.37

24 -- 4 21.4 1.50 1.48

26 -- 3 22.9 1.61 1.58

“/hg Kg/cm@@@@ Bar

Psig Kg/cm@@@@ Bar

Vacuum

Temperature Pressure

F C

28 -- 2 24.5 1.72 1.69

30 -- 1 26.1 1.84 1.80

32 0 27.8 1.95 1.92

34 1 29.6 2.08 2.04

36 2 31.3 2.20 2.16

38 3 33.2 2.33 2.29

40 4 35.1 2.47 2.42

45 7 40.1 2.82 2.76

50 10 45.5 3.20 3.14

55 13 51.2 3.60 3.53

60 16 57.4 4.04 3.96

65 18 64.1 4.51 4.42

70 21 71.1 5.00 4.90

75 24 78.7 5.53 5.43

80 27 86.7 6.10 5.98

85 29 95.3 6.70 6.57

90 32 104.3 7.33 7.19

95 35 114.0 8.01 7.86

100 38 124.2 8.73 8.56

105 41 135.0 9.49 9.31

110 43 146.4 10.29 10.09

115 46 158.4 11.1 4 10.92

120 49 171.2 12.04 11.80

125 52 184.6 12.98 12.73

130 54 198.7 13.97 13.70

135 57 213.6 15.02 14.73

140 60 229.2 16.11 15.80

145 63 245.6 17.27 16.93

150 66 262.9 18.48 18.13

155 68 281.1 19.76 19.37

Psig Kg/cm@@@@ Bar

4-15 T-312

SECTION 5

ELECTRICAL SCHEMATIC DIAGRAMS

5.1 INTRODUCTION

This section contains Electrical Schematic Diagrams covering the Models listed in Table 1-1. Contact your Carrier
Transicold service representative or call the technical hot line at 800--450--2211 for a copy of the schematic for your
specific model.

5-1

T-312

ATHRUK

1
2
3

LTHRUY

P ACKARD CONNECTOR

Figure 5-1. Electrical Schematic Diagram Legend and Symbols

(Based On Drawing No. 62-10907 Rev ---)

T-312

COACH INTERFACE

CONNECTOR

5-2

CONDENSER

**DRIVER CONTROL BOX

MAIN EVAPORATOR

DRIVER EVAPORATOR

PARCEL RACK (ROAD SIDE)

PARCEL RACK (CURB SIDE)

NOTE

In 2003, early production units were retrofitted with diodes. If servicing a unit that is not wired as
shown above, the unit should be retrofitted. Contact Carrier Service Engineering.

See Figure 5-1 for legend and symbols.

Figure 5-2. Electrical Schematic Diagram, Sheet 1 of 2

(Based On Drawing No. 62-10907 Rev ---)

5-3

T-312

Figure 5-3. Electrical Schematic Diagram, Sheet 2 of 2

(Drawing No. 62-10907 Rev---)

T-312

5-4

Figure 5-4. Electrical Schematic Diagram

(Contact vehicle manufacturer for a specific diagram)

5-5

T-312

INDEX

A

Air Conditioning Refrigerant Cycle, 1-12

AirFilter,3-6,4-14

C

Checking For Noncondensibles, 4-6

Checking High Pressure Switch, 4-7

Checking Refrigerant Charge, 4-6

Compressor, 1-3, 1-4

Compressor Oil Level, 4-10

Compressor Re--install, 4-9

Compressor Removal, 4-8

Compressor Unloaders, 4-9

Condenser Assembly, 1-2, 4-13

Condenser Coil, 4-13

Condenser Motor, 4-13

H

Heating Flow Cycle, 1-11

Humidity Control, 2-5

Humidity Sensor, 4-11, 4-12

I

Installing Manifold Guages, 4-2

Introduction, 1-1

M

Main Control Box, 1-7

Main Controller Auto Control Sequence, 2-4

Main Evaporator Assembly , 1-6

Main Evaporator Blower Assembly, 4-12

Main Evaporator Or Heater Coil, 4-13

Maintenance Schedule, 4-1

Microprocessor Error Message Definition, 3-1

D

Display Error Message Definition, 3-1

Driver A/C Switch, 1-9, 2-2

Driver Control Box, 4-13

Driver Display Alarm Message, 3-1

Driver Display Panel, 1-8, 2-1

Driver Evaporator, 4-14

Driver Evaporator, 1-5

Driver Evaporator--Blower, 4-14

E

Electrical Specifications -- Controls, 1-9

Electrical Specifications -- Motors, 1-9

Electronic Control Data Flow, 1-14

Evacuation And Dehydration, 4-4

Evaporator Assemblies, 1-4

Evaporator Coils, 1-12

F

Filter--Drier, 4-7

O

Oil Charge, 1-9

Oil: Adding Charge, 4-10

Operating Controls, 1-8

P

Parameter Codes, 3-4

Parcel Rack Evaporator, 4-14

Parcel Rack Evaporator, 1-5

Parcel Rack On/Off, 1-8, 2-2

Pressure Transducer, 4-11, 4-12

R

Refrigerant Charge, 1-9, 4-6

Refrigerant Charge Removal, 4-3

Refrigerant Leak Check, 4-4

Refrigerant Removal From Compressor, 4-3

Refrigerant Service Connections, 4-5

Refrigeration System Components, 1-9

Replacing High Pressure Switch, 4-7

Index-1 T-312

INDEX

S

Safety Devices, 1-10

Safety Summary , General, i

Schematic Diagram, 5-3, 5-4, 5-5

Servicing Motor Brushes, 4-12

Suction and Discharge Service Valves, 4-1

Superheat -- Check/Measure, 4-8

System Pumpdown, 4-2

System Service, 4-1

T

Temperature Pressure Chart, 4-15

Temperature Sensor, 4-11

Thermostatic Expansion Valve, 4-7

TroubleShooting, 3-1

Troubleshooting Proceedures, 3-5

Index-2T-312