Carrier CAPRI-280 Operation And Service Manual

Bus Air
Conditioning
Equipment

Model
CAPRI-280
Septa

T-283

OPERATION AND

SERVICE MANUAL

BUS

AIR CONDITIONING

UNIT

Model CAPRI-280

Carrier T ransicold Division, Carrier Corporation,P.O. Box 4805, Syracuse, N.Y. 13221

Carrier Corporation 1997 D Printed in U. S. A. 1097

Septa

TABLE OF CONTENTS

Section Page

SAFETY SUMMARY 1.......................................................

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

1.1 Introduction 1-1...............................................................

1.2 General description 1-2........................................................

1.2.1 Condenser Unit 1-2...................................................

1.2.2 Evaporator Unit 1-3...................................................

1.2.3 Compressor Assembly 1-4.............................................

1.3 Refrigeration System Component Specifications 1-4...............................

1.4 Electrical Specifications ECDC Motors 1-4........................................

1.5 Electrical Specifications --- Controller Input Sensors and Transducers 1-4.............

1.6 Safety Devices 1-4.............................................................

1.7 Air Conditioning Refrigerant Cycle 1-5............................................

1.8 Heater Flow Cycle 1-6..........................................................

1.9 Relay Board --- Electronically Commutated DC Motors with 2-speed Input Signal 1-7...

1.10 Logic Board 1-8...............................................................

1.11 Control Panel (Diagnostic Module) 1-9...........................................

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

2.1 Starting, Stopping and Operating Instructions 2-1.................................

2.1.1 HVAC Power to Controller 2-1..........................................

2.1.1 Starting 2-1..........................................................

2.1.3 Self-Test and Diagnostics (Check for Errors and/or Alarms) 2-1.............

2.1.4 Stopping 2-1.........................................................

2.2 Pre-Trip Inspection 2-1.........................................................

2.3 System Operation 2-1..........................................................

2.3.1 Temperature Control 2-1...............................................

2.3.1.1 Capacity Control 2-1........................................

2.3.1.2 Cooling/Reheat 2-3.........................................

2.3.1.3 Heating 2-3................................................

2.3.2 Boost Pump 2-3......................................................

2.3.3 Compressor Unloader Control 2-3......................................

2.3.4 Evaporator Fan Speed Selection 2-3....................................

2.3.5 Condenser Fan Speed Control 2-3......................................

2.3.6 Compressor Clutch Control 2-3.........................................

2.3.7 Alarm Description 2-4.................................................

2.3.8 Hour Meters 2-4......................................................

2.4 Microprocessor Diagnostic Service Tool (MDST) 2-4...............................

2.4.1 Connecting 2-4.......................................................

2.4.2 Control 2-4...........................................................

2.4.3 Setpoint Change 2-4..................................................

2.4.4 Mode Keys 2-4.......................................................

2.4.4.1 Cool 2-4...................................................

2.4.4.2 Heat 2-4...................................................

2.4.4.3 Vent 2-4...................................................

2.4.5 Fan Key 2-4..........................................................

i

2.4.6 Temperature Key 2-4..................................................

2.4.7 Diagnostic Mode 2-4..................................................

2.4.8 System Parameters 2-5................................................

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

3.1 Self Diagnostics 3-1...........................................................

3.2 System Alarms. 3-1............................................................

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

4.1 Maintenance Schedule 4-1.....................................................

4.2 Suction And Discharge Service V alves 4-1........................................

4.3 Installing Manifold Gauges 4-1..................................................

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 4-2...................................

4.5 Refrigerant Leak Check 4-2.....................................................

4.6 Evacuation And Dehydration 4-3................................................

4.7 Adding Refrigerant To System 4-3...............................................

4.7.1 Checking Refrigerant Charge 4-3.......................................

4.7.2 Adding Full Charge 4-3................................................

4.7.3 Adding Partial Charge 4-4..............................................

4.8 Checking For Noncondensibles 4-4..............................................

4.9 Checking And Replacing High Pressure Cutout Switch 4-4.........................

4.9.1 Checking High Pressure Switch 4-4.....................................

4.9.2 Replacing High Pressure Switch 4-4.....................................

4.10 Filter-drier 4-5.................................................................

4.11 Thermostatic Expansion Valve 4-5...............................................

4.12 Model 05G Compressor Maintenance 4-6........................................

4.12.1 Removing the Compressor 4-6.........................................

4.12.2 Compressor Oil Level 4-7..............................................

4.12.2.1 Checking the Compressor Oil Level 4-7........................

4.12.2.2 Adding Oil with Compressor in System 4-7.....................

4.12.2.3 Adding Oil to Service Replacement Compressor 4-8............

4.12.2.4 Removing Oil from the Compressor 4-8........................

4.13 Temperature Sensor Checkout 4-8...............................................

4.14 Suction And Discharge Pressure Transducer Checkout 4-8.........................

4.15 Replacing Sensors and Transducers 4-9.........................................

4.16 Controller Configuration 4-19.....................................................

ii

5 ELECTRICAL 5-1.............................................................

5.1 Introduction 5-1...............................................................

LIST OF ILLUSTRATIONS

Figure Page

1-1. A/C Component Identification 1-1...............................................

1-2. Condenser Unit 1-2............................................................

1-3. Evaporator Unit 1-3............................................................

1-4. Heater Flow Diagram 1-6.......................................................

1-5. RelayBoard 1-7...............................................................

1-6. Logic Board 1-8...............................................................

1-7. DiagnosticModule 1-9.........................................................

2-1. Auto Reheat Mode 2-2.........................................................

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

4-2. Manifold Gauge Set 4-2........................................................

4-3. Checking High Pressure Switch 4-4..............................................

4-4. Thermostatic Expansion Valve 4-5...............................................

4-5. Thermostatic Expansion Valve Bulb and Thermocouple 4-5.........................

4-6. Removing Bypass Piston Plug 4-7...............................................

4-7. Model O5G Compressor 4-7....................................................

5-1. Electrical Wiring Schematic Diagram 5-2.........................................

LIST OF TABLES

Table Page

2-1. Main Evaporator Fan Speed Relay Operation 2-3..................................

2-2. ParameterCodes 2-5..........................................................

3-1. Error Codes 3-1...............................................................

3-2 Alarm Codes 3-2..............................................................

3-3. General System Trouble Shooting Procedures 3-4.................................

4-1. Temperature Sensor (AT, TSC, TSD and TSR) Resistance 4-8.......................

4-2. Suction and Discharge Pressure Transducer (SPT and DPT) Voltage 4-9.............

4-3. Controller Configuration 4-10.....................................................

4-4. R-134a Temperature - Pressure Chart 4-11.........................................

iii

SAFETY SUMMARY

GENERAL SAFETY NOTICES

Thefollowinggeneralsafetynoticessupplementthe specificwarningsand cautionsappearingelsewherein
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
followingthree sectionslabeled:First Aid,OperatingPrecautionsand MaintenancePrecautions.Alisting
ofthespecific warningsandcautions appearingelsewhereinthe manualfollows thegeneralsafetynotices.

FIRST AID

An injury, no matter howslight, shouldnevergo unattended. Alwaysobtain first aid or medicalattention
immediately.

OPERATING PRECAUTIONS

Always wear safety glasses.
Keep hands, clothing and toolsclear of the evaporator and condenser fans.
Noworkshouldbeperformedonthe unituntilallcircuitbreakersand start-stopswitchesareturnedoff,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
grilleor evaporatoraccesspanelsbeforeturningpoweroff,anddisconnectingandsecuringthe powerplug.

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

Do not bypass any electricalsafety devices, e.g. bridging an overload, or using any sort of jumper wires.
Problems with the systemshould be diagnosed, and any necessaryrepairs performed, by qualified service
personnel.

When performingany arc weldingonthe unit,disconnectallwire harness connectors fromthemodules in
the controlbox.Donotremove wire harness from the modulesunless you aregroundedto the unit frame
with a static-safe wriststrap.

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

(never use water).

2

1

SECTION 1

DESCRIPTION

1.1 INTRODUCTION

ThismanualcontainsOperating andService Instructions
and Electrical Data for the Model Capri 280 Air
Conditioning and Heating equipment furnished by
Carrier Transicold Division.

The Capri 280 consists of a condenser, evaporator and

3

2

1

compressor.The airconditioningandheatingequipment
interfaces with electrical cabling, refrigerant piping,
engine coolant piping for heating, ductwork and other
components furnished by the bus manufacturer to
completethesystem.

7645

8

9

Figure 1-1. A/C Component Identification

1. Compressor

2. Pressure Switches

3. Electrical Control and Relay Board

4. Evaporator Section

5. Evaporator Blowers and Motors

6. Condenser Axial Fan/Motor Assemblies.

7. Condenser Section

8. Main Harness

9. Power Harness

10. Alternator

11. Power Relay

1-1

T-283

1.2 General description

1.2.1 Condenser Unit

The condenser unit includes condenser coils, fan and
motor assemblies, filter-drier, receiver, liquid line
solenoidvalve,kingvalves, discharge check valve, andan
ambient temperaturesensor.

The condenser coils provide a heat transfer surface for
condensing refrigerant gas at a high temperature and
pressure into a liquidat 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-drierremovesmoisture andothernoncondensibles
from the liquid refrigerant before it enters the thermal
expansion valves in the evaporator assembly.

The receiver collects and stores liquid refrigerant. The
receiver is fitted with upper and lower liquid level sight
glasses to enable determining refrigerant liquid level in
thereceiver. Thereceiverisalsofitted witha fusibleplug
which protects the system from unsafe high refrigerant
temperatures. Themain liquid linesolenoid valvecloses
whensystemisshutdowntopreventfloodingofcoils with
liquid refrigerant and to isolate the filter-drier for
servicing when the compressor is shut down. The king
valves enable servicing of the filter-drier. The ambient
temperature sensormeasures ambient temperature and
sends an electrical signal to the controller.

The discharge line check valve is a spring loaded,
normally closed valve that opens with the flow of
refrigerant from the compressor. When the compressor
clutchisdisengaged,the discharge checkvalvewill close,
preventing the flow of high pressure liquid from the
condenser to flow back into the compressor.

1. Condenser Coil

2. Condenser Fan Motor Assembly

3. Receiver Tank

4. Service Valve

5. Filter Drier

6. Liquid Hose

7. Gas Hose

8. Condenser Motor Harness

9. Condenser Motor Plate

10. Lid Screw Nut

11. Locking Screw Gasket

12. Lid Bolt Support

T-283

Figure 1-2. Condenser Unit

13. Square Nut

14. Locking Screw Gasket

15. Right Front Grille

16. Left Front Grille

17. Right Front Lateral Grille

18. Left Front Grille

19. Right Rear Lateral Grille

20. Left Rear Lateral Grille

21. Condenser Fiberglass Base

22. Condenser Top Cover Lid

23. Liquid Line Solenoid Valve

24. Receiver Tank Support

1-2

1.2.2 Evaporator Unit

The evaporator unit includes roadside and curbside
evaporator coils.

Each evaporator unit includes six fan and motor
assemblies, evaporator/heater coil assemblies, thermal
expansion valves, condensate drain connection(s), and
evaporator heat valve.

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;thusprovidingcoolingwhenrequired.Theheating

coilsprovideaheat transfer surfacefortransferringheat
fromengine coolantwater circulating insidethetubes to
air circulating overtheoutside surfaceofthe tubes,thus
providing heating when required. The fans circulate the
air over the coils. The air filtersfilter dirt particlesfrom
the air before the air passes over the coils. The thermal
expansion valves meter the flow of refrigerant entering
the evaporator coils. The heat valve controls the flow of
engine coolant water supplied to the heating coils upon
receipt of a signal from the controller. The condensate
drainconnectionsprovide ameans forconnecting tubing
for disposing of condensate collected on the evaporator
coilsduring cooling operation.

1. Evaporator Coil, Roadside

1a. Evaporator Coil, Curbside

2. Expansion Valve

3. Evaporator Blower and Motor

3a. Allen Screw

4. Humidity Sight Glass

5. Return Air Filter

6. Liquid Line

7. Relay Board

8. Logic Board

Figure 1-3. Evaporator Unit

10. Discharge Line

11. Heating Line

12. Evaporator Motor Harness

13. Lid Screw --- Stopper

14. Locking Screw Gasket

15. Lid Bolt Support

16. Square Nut

17. Lid Locking Screw

1-3

9. Suction Line

T-283

1.2.3 Compressor Assembl y

The compressor assembly includes the refrigerant
compressor, clutch assembly, suction and discharge
service valves, high pressure switch, low pressure switch,
suction and discharge servicing (charging) ports and
electricsolenoid unloaders.

The compressor raises the pressure and temperature of
the refrigerant and forces it into the condenser tubes.
The clutch assembly provides a means of belt drivingthe
compressorby thebusengine. Thesuctionand discharge
servicevalvesenableservicingofthecompressor.Suction
anddischarge servicing(charging)portsmountedonthe
service valves enable connection of charging hoses for
servicing of thecompressor, as well as otherpartsofthe
refrigerant circuit. The high pressure switch contacts
open on a pressure rise to shut down the system when
abnormallyhighrefrigerant pressuresoccur.Theelectric
unloaders provide a means of controlling compressor
capacity,whichenablescontroloftemperatureinsidethe
bus. For more detailed information on the compressor,
refer to manual number 62-02756.

1.3 REFRIGERATION SYSTEM COMPONENT
SPECIFICATIONS

a. Refrigeration Charge

R-134a: 11.3 lb (5.1 kg)

b. Compressor

Model: 05G
No. of Cylinder: 6
Weight (Dry): 165 lb (75 kg)
Oil Charge:

New Compressor: 6.75 pints (3.2liters)
Replacement Compressor:5.5 pints (2.6 liters)

Oil Level:

Levelinsightglassbetween Min.---Maxmarkson
compressor crankcase (curbside)

Approved Compressor Oils - R-134a:

Castrol: Icematic SW68C
Mobil: EALArctic 68
ICI: Emkarate RL68H

c. Thermostatic Expansion Valve - for R-134a

Units:

Superheat Setting(Non-externallyadjustable): 10

to 12_F

MOP Setting (Nonadjustable): 55 4psig(375 

28.5 kPa)

d. High Pressure Switch (HPS) - for R-134a

Units:

Opens at: 300 10 psig
Closes at: 200 10 psig

1.4 ELECTRICAL SPECIFICATIONS ECDC MOTORS
a. Evaporator/Heater Blower (Fan) Motor

FullLoad Amps (FLA): 8.4A
Horsepower:0.34
Voltage:24vdc
Operating Speed: 4375 rpm

b. Condenser Fan Motor

Bearing Lubrication: Shell Dolium R
Horsepower:0.15hp
FullLoad Amps (FLA): 7A
Operating Speed: 3180 rpm
Voltage:24vdc

1.5 ELECTRICAL SPECIFICA TIONS -­Controller Input Sensors and Transducers

a. Suction and Discharge Pressure Transducer

Supply Voltage: 4.5 to 5.5 vdc (5 vdcnominal)
Supply current: 8 mA maximum
Output Range: 8K ohms minimum
InputRange: ---6.7to450psig(---46.2kPa to 3.1 mPa)
Output Current: -1.5 mA minimum to

1.5 mA maximum

Output Voltage: vdc = 0.0098 x psig

+ 0.4659 (Se e Table 4-2 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 4-1 for calculations.)

1.6 SAFETY DEVICES

System components are protected from damage caused
byunsafeoperatingconditionswithsafetydevices.Safety
devices with Carrier Transicold supplied equipment
include high pressure switch(HPS), low pressure switch
(LPS), circuit breakersand fuses.

a. Thermal Switches

Condenser Motor Overloads

Each condenser fan motor is equipped with an internal
thermalprotector switch, condensermotor overloads. If
excessivemotortemperatureexists,thecondensermotor
overload switch will open to de-energize the
corresponding condenser fan.

Evaporator Motor Overloads

The evaporator fan motors are equipped with internal
thermal protector switches. If excessive motor
temperature exists, the switch will open to de-energize
the corresponding evaporator fan; this will prevent the
affected evaporator motor fromoperating.

T-283

1-4

b. Pressure Switches

High PressureSwitch (HPS)

During the A/C mode, HVAC system operation will
automaticallystopiftheHPSswitchcontactsopen dueto
an unsafe operating condition. Opening HPS contacts
de-energizes,throughthecontroller,theA/Ccompressor
clutchand condenserfanmotor relaysshutting downthe
system.

The high pressure switch (HPS)isinstalledinthecenter
head of the compressor and opens on a pressure rise to
shut down the system when high pressure conditions
occur. For R-134a systems, the switch is factory set to
open at 300 10 psig and close at 200 10 psig.

Low Pressure Switch (LPS)

Thelowpressureswitchisinstalled inthecompressorand
opensona pressuredrop toshutdownthesystemwhena
low pressure condition occurs. For R-134a systems, the
switchisfactorysetto openat63psig.In addition,ifthe
control monitors a pressure less than 10 psig by the
suction pressure transducer mounted in the evaporator
section, the system will be shut down for at least one
minute.

c. Fuses and Breakers

All outputs from the relay board are protected against
high current by circuit breakers. Independent 15 amp
circuitbreakersprotecteachmotor.Inaddition,a 15amp
fuse protects a motor from over current. During a hi gh
current condition, the breaker or fuse may open. When
the breaker opens, power will be removed from the
device and a breaker alarm will be generated. When a
fuseopens, groundwillbe removedfromthedevice anda
motor alarm will be generated.

d. Ambient Lockout

The ambient temperature sensor located in the
condenser section measures the condenser air
temperature.Whenthetemperatureislessthan45F, the
compressorislocked outuntilthe temperature increases
above 50F to prevent compressor damage.

system using R-134a as a refrigerant. The main
components of the system are the reciprocating
compressor, air-cooled condenser coils, receiver,
filter-drier, thermostatic expansion valves, liquid line
solenoid valve and evaporator coils.

The compressorraisesthe pressure and thetemperature
of the refrigerant and forces it into the condenser tubes.
Thecondenserfan circulatessurrounding air(whichis at
a temperature lower than the refrigerant) over the
outside of the condenser tubes. Heat transfer is
established fromthe refrigerant (insidethe tubes)tothe
condenser air (flowing over the tubes). The condenser
tubeshavefinsdesignedtoimprovethetransferofheat
from the refrigerant gas to the air; this removal of heat
causes the refrigerant to liquefy, thus liquid refrigerant
leaves the condenserandflows to the receiver.

The receiver serves as a liquid refrigerant reservoir so
that a constant supply of liquid is available to the
evaporatorsasneeded, and acts asastorage spacewhen
pumping down thesystem.The receiverisequippedwith
sightglassesto observethe refrigerantfor restrictedflow
and correct charge level.

The refrigerant leaves the receiver and passes through
the receiver outlet/service valve, through a filter-drier
where an absorbent keeps the refrigerant cleananddry.

Fromthe filter-drier, the liquid refrigerant then flowsto
the thermal expansion valves which reduce pressure and
temperature of the liquid and meters the flow of liquid
refrigerant to the evaporator to obtain maxi mum use of
the evaporator heat transfer surface.

The lowpressure,lowtemperature liquid that flowsinto
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
evaporatorair (flowingover thetubes) tothe 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 bus. Liquid line solenoid valvesclose
during shutdown to prevent refrigerant flow.

1.7 AIR CONDITIONING REFRIGERANT CYCLE

When air conditioning (cooling) is selected by the
controller, the unit operates as a vapor compression

The transfer of heat from the air tothelowtemperature
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.

1-5

T-283

Figure 1-4. Heater Flow Diagram

1.8 HEATER FLOW CYCLE

Heating circuit components furnished by Carrier
Transicold include heater cores and evaporator heat
valves for each evaporator assembly. Components
furnished by the bus manufacturer include auxiliary
heater and engine water pumps. The controller
automaticallycontrolsthe heatvalvesduringheatingand

T-283

reheat cycles to maintain required temperatures inside
the bus. Engine coolant (glycol solution) is circulated
through the heating circuit by the engine and auxiliary
waterpumps. Whenthe evaporator heat valvesolenoid
isenergized,thevalvewillopentoallowengine coolantto
flowthrough theheater coil(see Figure 1-4).Thevalveis
normallyclosedso thatifafailureoccurs,it willbe ableto
cool.

1-6

1.9 Relay Board -- Electronically Commutated DC Motors with 2-speed Input Signal

+

13

K1

1

K3

2

K2

D2 D6 D14 D17 D26 D37 D38 D41

---

EF2 EF1

4

EF3 EF4

3

K4

5
6

D81

EF HIGH
SIGNAL

EF6 EF5

K7

K8

10

7
8
9

K6

CF2 CF1

CF2 CF2

K9

K10

K24 K22 K21 K23

11

12

D85

CF

HIGH

SIGNAL

CF6 CF5

Figure 1-5 Relay Board

K14

K16
K18

K19

JP1

K15

K17
K20

K13

JP6

JP5

JP4

JP3

D57
D54
D63
D60
D72
D66
D51
D69

JP2

a. Relays

K1 Energizes evaporator fans 1 & 2.
K2 Energizes evaporator fans 3 & 4.
K3 Energizes evaporator fan 5.
K4 Energizes evaporator fan 6.
K5 Provides the evaporator fan high output

signal.

K 6 Provides the condenser fan high output

signal. (Not used).
K 7 Energizes condenser fans 1 & 2.
K 8 Energizes condenser fans 3 & 4.
K9 Notused
K10 Not used
K13 Energizes the A/C clutch.
K14 Energizes unloader 1.
K15 Energizes unloader 2.
K16 Energizes the high low pressure failure.
K17 Energizes the heat solenoid valve.
K18 Energizes the alarm output.
K19 Energizes the booster pump.
K20 Energizes the motor fail light.

b. Thermal Circuit Breakers 24V

CB 1 Evaporator fan #1. 15 Amp.
CB 2 Evaporator fan #2. 15 Amp.
CB 3 Evaporator fan #3. 15 Amp.
CB 4 Evaporator fan #4. 15 Amp.
CB 5 Evaporator fan #5. 15 Amp.
CB 6 Evaporator fan #6. 15 Amp.
CB 7 Condenser fan #1. 15 Amp.
CB 8 Condenser fan #2. 15 Amp.
CB 9 Condenser fan #3. 15 Amp.
CB10 Condenser fan #4. 15 Amp.
CB11 Spare. 15 Amp.
CB12 Spare. 15 Amp.
CB13 A/c clutch, unloaders 1&2

motor fail, heat valve, pressure fail

&spareoutput. 15Amp.

c. Connectors

EF1-EF6 Evaporator Fans.
CF1-CF4 Condenser Fans.
JP1 External evaporator & condenser fan

thermal overload connections.
JP2 Logic board connector.
JP3 Booster pump.
JP4 A/C Clutch, Pressure fault output,

Compressor High Pressure Switch.
JP5 High pressure fail, motor fail output,

heat valve.
JP6 Unloaders 1 & 2.
EF-HIGHSIGNAL Output to the evaporator

fans to operate on high
speed.

CF-HIGH SIGNAL Output to condenser fans to

operate on high speed.
(Not used)

d. LEDS

D 2 Evaporator fans 1 & 2 are energized.
D 6 Evaporator fans 3 & 4 are energized.
D14 Evaporator fan 5 is energized.
D17 Evaporator fan 6 is energized.
D26 Condenser fans 1 & 2 energized.
D30 Condenser fans 3 & 4 energized.
D38 Condenser fans 5 & 6 energized. (Not used).
D51 A/C clutch output active.
D54 Unloader 1 output active.
D57 Unloader 2 output active.
D60 High low pressure failure.
D63 Heat valve output active.
D66 Alarm output active.
D69
D72 Motor fail light.
D81 Evaporator fans on high.
D85 Condenser fans on high. (Not used).

1-7

T-283

1.10Logic Board

J1 Logic board power in.
J2 Display interface.
J3 Manual control inputs.
J4 Interlock Inputs

(WTS, low side pressure switch etc.)
J5 Relay board interface.
J6 Sensor inputs (Thermistors, etc.).

T-283

Figure 1-6 Logic Board

J7 Diagnostics interface (RS232, DB9).
D2 Blinks once per second in normal operation.

On steady to indicate alarms detected.

D3 Off In normal operation, blinks out alarm

codes (2 digits each) when alarms detected.

1-8

1.11Control Panel (Diagnostic Module)

12

3

5

6

4

7

91011

8

1. Display

2. Down --- decrease selection

3. Up --- increase selection

4. Ventilation

5. Auto Control Selection

6. Air Conditioning

Figure 1-7. Diagnostic Module

7. Heating

8. Fan Speed Selection

9. Not used

10. Temperature Inside / Outside

11. Turn On / Turn Off

1-9

T-283

SECTION 2

OPERATION

2.1 STARTING, STOPPING AND OPERATING
INSTRUCTIONS

2.1.1 HVAC Power to Controller

Before starting the system, electrical power must be
available from the bus power supply. The HVAC
controller receives power from two sources:

a. 24 vdc power for the microprocessor electronics

is supplied throughthebusmultiplexmodule.

b. 24vdc, 125amp,powerfrom afuse inthe battery

compartment supplies power which controls
relays, clutch and unloader solenoids in the
compressor, evaporator and condenser
assemblies; thispower iscontrolledbythe HVAC
controller.

2.1.2 Starting

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

After the engine is started place the A/C switch
locatedonthedashin theonposition. All system
controls will operate automatically in heating,
cooling or ventilating mode, as required.

2.1.3 Self-Test and Diagnostics

(Check for Errors and/or Alarms)

Self-test of the main controller electrical circuit is
automatically initiated when the system is first
powered up. If there is an error in the circuit, ER‘‘x”
willbeindicatedbyflashingtheerrorcodeonboththe
statusandcodeLED’ssimultaneously. Ifadiagnostic
module is connectedtothe controller, the error code
canalsobe readonthe display. Ifthereare noerrors
in the circuit, system will operate normally and flash
the status LED at a one second interval. During
normal operation, the controller monitors system
operating parametersfor outoftolerance conditions.
If an out of tolerance condition occurs, ALARM will
be indicated through the code LED or on the
diagnostic tool display. If an alarm condition exists,
diagnosticscanbemanuallyinitiatedtoisolatesystem
fault(s) by simultaneously pressing the up and down
keys continuously for five seconds to view more

information. Refer to section 3 for definition of
systemerrorsandalarmsandgeneraltroubleshooting
procedures.

2.1.4 Stopping

Withthesystemoperating,switching theACswitchto
the offposition will stoptheHVAC systemoperation
by removing power to the logic module.

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

motors.

b. Check compressor oil level. (Refer to section

4.12.2.)
c. Check refrigerant level. (Refer to section 4.7.1.)
d. Ensure that self-test has been successfully

performedand thatthereare noerrors oralarms
indicated. (Referto section 2.1.7.)

2.3 SYSTEM OPERATION

2.3.1 Temperature Control

Temperature is controlled by maintaining the return
air temperature measured at the return air grille.

2.3.1.1 Capacity Control

The controller automatically compares system
temperatures with the controller setpoints and
changes system operating modes at certain
temperature deviations. Figure 2-1 shows various
changes in operating modes and controller actions at
various temperature deviations from controller
setpoint. Upon rising temperature, mode changes
occur when temperatures are above those given in
Figure 2-1 above controller setpoints, On a falling
temperature, mode changes occur when
temperaturesarebelowthosegiveninFigure2-1.The
system will operate in these modes unless pressures
override the controller settings.

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2-1

Cool

High Speed

Loaded

Cool

High Speed

4 Cylinders

Cool
High Speed
2 Cylinders

Reheat
High Speed
2 Cylinders

T-283

Heat

Low Speed

Heat

High Speed

Figure 2-1. Auto Reheat Mode

2-2

2.3.1.2 Cooling/Reheat

Cooling and reheat require various combinations of
compressor unloading. Cooling is accomplished by
energizing the compressor and condenser fans,
opening the liquid solenoid valve and closing the
heating valve. Reheat opens the heat valve while
cooling. This allows for reduced capacity around
setpoint and de-humidification.

2.3.1.3 Heating

Duringheating,theliquidsolenoidisclosedtostop
cooling and the compressor and condenser fans will
shut down. The fan speed will vary based on the
temperature difference from setpoint. Heating will
notstartuntil theenginecoolant switch(ECS)closes.
The ECS is located on the block of the vehicle andis
provided by the OEM. It senses the engine coolant
temperature. The switch closes at 105Fon
temperature rise.Theswitch prevents thecirculation
of cooler air throughout the vehicle during initial
start-up.

2.3.2 Boost Pump

When the unit is in heat the boost pump relay is
energized. This signal is read by the bus multiplex
system to activate the boost pump.

2.3.3 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
Model 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
withtwo,fourorsixcylinders.Whenthecompressoris
off, the unloaders 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 may be
de-energized, if required. Any subsequent changes
between energizing and de-energizing theunloaders
must be staged with a two second delay. Only one
unloader may change state at a time when staging is
required.

secondcompressorcylinderbank(twocylinders);
this output will remain energized until the
pressure increases to above31psig.

b. Discharge Pressure

Head Pressure is also controlledby the unloaders:

1. CompressorUnloaderUV1Relay.

When the
discharge pressure increases above 275 psig, the
first compressor unloader is energized; this
output will remain energized until the pressure
decreases below 220 psig. Staging is ignored for
energizing the unloader due to discharge
pressure overrides.

2. CompressorUnloaderUV2Relay.

When the
discharge pressure increases above 285 psig, the
second unloader is energized; this output will
remain energized until the pressure decreases
below 225 psig.

2.3.4 Evaporator Fan Speed Selection

Each air conditioning unit is equipped with six two
speedfan motors.Temperaturecontrolis theprimary
method of determining the fan speed selection. The
following table indicates relay operational status for
the various fan motor states.

Table 2-1. Main Evaporator Fan Speed

Relay Operation

STATE

HIGH

SPEED

EVAP FAN

RELAYS

RELAY

Off Off Off

Low Off On

High On On

Theevaporatorfans wills tart in lowspeed andrunin
high speed for cool and reheat modes. During heat
modethe fanswill runin eitherhighorlowspeed(see
figure 2-1).

Exceptions to the above are as follows:

a. In the event that the coolant temperature switch

is open, the evaporator fans are kept off during
heating.

a. Suction Pressure

In addition to temperature control, the electric
unloaders will be used to preventcoil frosting:

1. CompressorUnloaderUV1Relay.
suctionpressuredecreasesbelow26psig,thefirst
unloader is energized unloading the first
compressor cylinder bank (two cylinders); this
output will remain energized until the pressure
increases to above 34 psig.

2. CompressorUnloaderUV2Relay.
suction pressure decreases below 23 psig, the
second unloader is energized unloading the

T-283

When the

When the

2.3.5 Condenser Fan Speed Control

The condenser fans are energized when the
compressor clutch output isenergized. Thefanswill
also be activated if a high pressure alarm has been
activated and operation has not been locked out
(refer to table3-3).

2.3.6 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 fromthecompressor. The
clutchwillbeengagedwhenin cooling.Theclutchwill

2-3

bedisengagedwhen thesystem isoff,wheninheating
or during high andlowpressure conditions.

The clutch coil is prevented from engagement when
the ambient temperature is below 45_F (7.2_C).

The clutch coil will be de-energized if the discharge
pressure rises to 300 psig, the setting of the
compressormountedhighpressureswitch.Theclutch
coil willenergizewhen thedischargepressure falls to
200 psig.

The clutch coil will be de-energized if the suction
pressure decreases below10 psig.

b. Connect theMDSTtothe service port locatedin

the return air section.
c. Unplug the logicboardconnector J3.
d. Turn the A/C main switch located in the driver’s

area back to the ON position.
e. Activatethesystembypressingthe1/0 keyon the

MDST panel.

NOTE

Be sure to reconnect J3 when testing is

completed or the system will fail to operate

when the MDST is disconnected.

2.3.7 Alarm Description

Alarm descriptions and troubleshooting procedures
are provided in section 3.

2.3.8 Hour Meters

An hour meter records the compressor run time
hours. The maximumhours is 999,999.
(Refer to table 3-2)

Anhourmeter recordsthetotal timetheevaporators
are on in hours. The maximum hours is 999,999.
(Refer to table 3-2)

2.4 MICROPROCESSOR DIAGNOSTIC
SERVICE TOOL (MDST)

TheMDSTis adiagnostic servicetool that allowsthe
user to interface with the microprocessor based
control. This allows system parameters, alarms and
settings to be viewed and modified.

2.4.1 Connecting

Connect the MDST harness to the service port
located in the return air section of the A/C system.
WhentheMDSTisconnected, thepanel lightswillbe
energized and the currently stored setpoint will be
displayed. If any alarm is active, the reading will be
Axx, where A indicates that the alarm is active and xx
indicates the alarm number.

2.4.2 Control

2.4.3 Setpoint Change

Setpoint may be changed by pressing up or down
arrow keys. The up key will increase the setpoint
temperature and the down key will decrease the
setpoint temperature.

NOTE

When modifying the setpoint temperature
for diagnostic purposes, be sure to reset the
setpoint when testing is complete.

2.4.4 Mode Keys

The mode keys allow the operation tobe selected as
auto,cool, heat,orvent.Thedefaultoperationisauto
asshowninFigure2-1.

2.4.4.1 Cool

The compressor is always operational in cool mode
unless overridden by safety device. Air conditioning
willrununtilsetpointisreachedatwhichtimetheheat
valve will open and reheatis performed.

2.4.4.2 Heat

The compressor will not operate in heat mode. The
heatvalveis openeduntil1_Fbelowsetpointatwhich
timethe heatvalve closesandthe evaporatorfans run
in ventilation.

2.4.4.3 Vent

In vent mode, only the evaporator fans operate.

NOTE

This procedure should be performed by an
HVAC educated technician who knows the
Carrier Capri 280 system design. Control
configuration is preset in by the
manufacturer and resetting of the
parameters should not be required. It is
recommended that Carrier Service or
Engineering is contacted before anycontrol
configuration is changed. Carrier can not be
responsible for changes made by the
customer whichcause system failure if there
has not been an opportunity to approve the
changes.

a. Turn the A/C main switch located in the driver’s

area to OFF.

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2.4.5 Fan Key

The fan key allows the evaporator fan speed to be
overridden to high or low. Theevaporator fan speed
willberesettoautowhenautomodekeyispressed.

2.4.6 Temperature Key

The temperature key allows the actual return air
ambient temperatures to be displayed.

2.4.7 Diagnostic Mode

Diagnostic mode can be entered by pressing the up
and down arrow keys simultaneously for 5 seconds.
Diagnostic mode allows alarms and system
parameters to be viewed. If there are any alarms
stored, the most recent alarm will beshown. To view
additionalalarm information,refer tosection3. Press
the up and down arrow keys to view parameters.

2-4

2.4.8 SYSTEM PARAMETERS

again indicate the setpoint setting. The parameters

are shown in Table 2-2. When scrolling through the
Pressingthe up/downarrowkeyswillallowtheuser to
scrollup ordown throughthe parameters.If nokey is
pressed for30secondsthismodeisexitedandthe
displaywillrevertbacktosetpoint.Pressingtheon/off
key any time will exit this mode and the display will

parameters, thecurrent parameter parameterwillbe

displayed for two seconds. After two seconds, the

display will show the data for the currentparameter.

When the last parameter is reached, the next

parameter will wrap back to one.

Table 2-2. Parameter Codes

CODE CODE NAME DESCRIPTION

P1 Return Air Temperature This value is the temperature measured by the return air sensor. If the sensor

P2 Coil Temperature This value is the coil temperature measured by the evaporatortemperature

P3 Ambient Temperature This value is the outside temperature measured by the ambient temperature

P4 Suction Line Tempera-

ture (not used)

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 thed ischarge pressure

P7 Superheat(notused) Not used.
P8 Analog Setpoint Tem-

perature (not used)

P9 A/C Control Window #1 This is the number of degrees F above setpoint at which theunloaders will be

P10 A/C Control Window #2 This is the number of degrees F above AC control window one at which the

P11 A/C Control Window #3 This is the number of degrees F above AC control window two at which the

P12 Heat Control Window This is the number of degrees F below setpoint before the heat valve is ener-

P13 Compressor Safety Off

Delay

P14 Fan Delay This is the minimum time (in seconds) that the fans must run at a particular

is shorted it will display CL. If it is open circuited it will display OP.

sensor. If the sensor is shorted it will display CL. If it is open circuited it will
display OP.

sensor. If the sensor is shorted it will display CL. If it is open circuited it will
display OP.

Not used.

er. If the sensor is shorted it will display CL If it is open circuited it will display
OP. If the auto key is pressed and held for five secondsthe suction pressure
will be calibrated to zero and the offset will be stored in no-volatile memory.
This calibration will be locked out if the offset is greater than 20 or lessthan

6.7 or if the clutch output is energized.

transducer. If the sensor is shorted it will display “CL” and if it is open circuited
it will display “OP”. If the auto key is pressed and held for five seconds the
suction pressure will be calibrated to zero and the offset will be stored in
non-volatile memory. This calibration will be locked out if the offset is greater
than 20 or less than 6.7 or if the clutch output is energized.

Not used.

both energized. This value can be modified between 0 and 10 degrees F. The
default value is 1 degree F.

first unloader will be energized. This value can be modified between 0 and 10
degrees F. The default value is 1 degree F.

evaporator fan speed will be set to low. This value can be modified between
0 and 10 degrees F. The default value is 1 degree F.

gized. This value can be modified between 0 and 10 degreesF. The default
value is 2 degree F for heat and 4 degrees F for reheat.

This number is the minimum timeinminutes that the compressor must be off
after a high or low pressure alarm before it can be restarted. This value can be
modified between one and five minutes. The default value is 1.

speed before changing to another speed. This value can be modified be­tween one and 60 seconds. The default value is two seconds.

T-283

2-5

Table 2-2. Parameter Codes --- Continued

Code Code Name Description

P15 Unloader/Heat Valve

Delay

P16 Compressor Head Pres-

sure Switch

P17 Condenser Fan Speed

Switch (not used)

P18 Maximum Setpoint This is the maximum value that the operatorwill be allowed to set the setpoint

P19 Minimum Setpoint This is the minimum value that the operatorwill be allowed to set the setpoint

P20 Compressor Hours High This is the number of hours of operation that the compressor has run with the

P21 Compressor Hours Low Thisis the number of hours of operation that the compressor has run with the

P22 Evaporator Hours High This is the number (in thousands) of hours of operation with the evaporator

P23 Evaporator Hours Low This is the number (in hundreds, tens and ones) of hours of operation with the

P24 Maintenance 1 Hour

High

P25 Maintenance 1 Hour

Low

P26 Maintenance 2 Hours

High

P27 Maintenance 2 Hours

Low

P28 Freeze Alarm Setting This is the value at which the freeze alarm will be activated. The default value

P29 RelayModuleVoltage This is the voltage being supplied to the relay module.
P30 Main Board Software

Version

P31 Display Software Ver-

sion
P32 Ki Not used.
P33 Kp Not used.

This is the minimum time (in seconds) that the unloaders and heat valve must
be in a particular state (open /closed) before changingtoanother state. This
value can be modified between 1 and 60 seconds. The default value is 2 sec­onds.

This is the current state of the compressorh ead pressure switch input. “CL”
will be displayed if it is closed and “OP” will be displayed if it is open.

Not used.

temperature. The value can be modified in degreeswiththeup and do wn keys
to a value between 60Fand80F.

temperature. The value can be modified in degreeswiththeup and do wn keys
to a value between 60Fand80F.

clutch energized in thousands

clutch energized in hundreds, tens and ones.

fans energized.

evaporator fans energized.
This is the value of compressor hours high (P20) at which maintenance alarm

#1 will be activated. This valuecan be modified by the up and down arrow
keys. If both high and low values are zero the alarm is disabled.

This is the value of compressor hours low (P21) at which maintenance alarm
#1 will be activated. This valuecan be modified by the up and down arrow
keys. If both high and low values are zero the alarm is disabled.

This is the value of evaporator fan hours high (P22)at which maintenance
alarm #2 will be activated. This value can be modified bythe up and down
arrow keys. If both high and low values are zero the alarm is disabled.

This is the value of evaporator fan hours low (P23)at which maintenance
alarm #2 will be activated. This value can be modified bythe up and down
arrow keys. If both high and low values are zero the alarm is disabled.

is 32F. This value can be modified between 20Fand40F in one degree in-
crements by using the arrow keys

This is the software version of the logicmodule.

This is the software version of the display module.

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2-6

SECTION 3

TROUBLESHOOTING

!

DO NOT UNDER ANY CIRCUMSTANCES
ATTEMPT TO SERVICE THE MICROPRO­CESSOR. SHOULD A PROBLEM DEVELOP WITH
THE MICROPROCESSOR, REPLACE IT.

3.1 SELF DIAGNOSTICS

Self testsareexecuted on powerupduring operation. Er­rors,ifany,willbeindicatedbythedisplayandtheunitwill
notbe allowedto operate.Thedisplay willindicateerrors

Table 3-1. Error Codes

Code NAME DESCRIPTION

ER 1 Data Memory Logic board data memory failure.
ER 2 Program Memory Logic board program memory failure.
ER 3 A/D A/D and multiplexer failure.
ER 4 Communication Failure Failure in communication between the logic board and MDST.
ER 5 Program Memory Display program memory failure.

3.2 SYSTEM ALARMS
a. Alarm codes

Alarms will be displayed by “AXX”, or “IXX” where“A”
indicates thatthe alarm isactiveand “I”indicatesthat the
alarmisinactive. Ifthe autokey is pressedthe displaywill
scroll through the three digit hour meter readings. If
multiple alarms are present the user can scroll through
eachalarm bypressing theautokey. Whentheendofthe
alarm lis t is reached the displa y will s how “--- --- --- ”. If the
auto ke y is held d own f or five s econds while “ --- --- --- ” is
displayed all inactive alarms are cleared.

with the code ER-X (X is the error number). The error
codes can also be read by counting the number of times
that the status and alarm LED’s flash simultaneously.

alarm is already present. Each alarm recorded will also
have an evaporator hour meter reading corresponding to
the activation time. When an alarm becomes inactive a
statusindicator inthe alarmqueue willchange toindicate
thatthe alarmis inactive.If anyalarms areactive thefault
output will be energized.

c. Alarm queue

The alarm queue consist of10alarmlocations.Whenthe
alarm queue is full an alarm will be generated but not
stored toindicated this. Whenalarmsare viewed this will
be the first alarm to be shown.

!CAUTION

b. Activation

When an alarm becomes active they will be placed in an
alarm queueinthe order at whichthey initiate unless the

T-283

d. Alarm clear

TheusermayclearinactivealarmsthroughtheMDST
keypad or computer communications.

3-1

Table 3-2. Alarm Codes

ALARM

NO.

11 Coil Freeze Coil temperature is less

12 High Voltage Thebatteryvoltageis

13 Low Voltage Thebatteryvoltageis

14 Return Air Probe Failure Return air temperature

15 Suction Pressure

Transducer Failure

16 Discharge Pressure

Transducer Failure

17 Low Pressure Shutdown Low suction pressure

21 High Discharge Pressure High discharge pressure

22 Breaker Trip Alarm A breaker on the relay

23 Evaporator Fan Overload Evaporator fan overload

24 Condenser Fan Overload Condenser fan overload

TITLE CAUSE REMEDY CONTROLLER

than 32Fandthecom­pressor is operating.

greater than 32 volts.

less than 17 volts.

sensor failure or wiring
defective.

Suction pressure trans­ducer failure or wiring
defective.

Discharge pressure
transducer failure or wir­ing defective.

switch open or wiring
defective.

switch open or wiring
defective.

board has tripped or a
fan relay has failed.

jumper is open.

jumper is open.

Check causes of coil
freezing. (Refer to sec­tion 3.5.6)

Check, repair or replace
alternator.

Check, repair or replace
wiring or alternator.

Ensure all connectors
are plugged in. Check
sensor resistance or wir­ing. Replace sensor or
repair wiring.

Ensure all connectors
are plugged in. Check
sensor voltage or wiring.
Replacesensororrepair
wiring.

Ensure all connectors
are plugged in. Check
sensor voltage or wiring.
Replacesensororrepair
wiring.

Check cause of low suc­tion pressure. (Refer to
section 3.5.3)

Check discharge pres­sure transducer reading,
wiring or cause of high
discharge pressure.
(Refer to section 3.5.3)

Check breakers for
tripped device. Repair
short and reset breaker.

Ensure connector is
plugged in or repair
wiring.

Ensure connector is
plugged in or repair
wiring.

RESPONSE

An alarm will be generated
and the system will shut­down. The evaporator fans
will remain running whilethe
compressor is off.

The system is shut down
until the voltage returns to
normal levels.

The system is shut down
until the voltage returns to
normal levels.

All outputs except the evap­orator fans will be de-ener­gized.

Both unloaders are ener­gized.

One unloader is energized.

The clutch is de-energized
for the minimum off time.
The evaporator fans will re­main running during this pe­riod. After the compressor
cycles off three times in 30
minutes all outputs will be
de-energized and the sys­tem is locked out until the
poweriscycledorthealarm
is reset through the keypad.

The clutch is de-energized
for the minimum off time.
The condenser and evapo­rator fans will remain run­ning during this period. Af­terthecompressorcycles
off three times in 30 minutes
all outputs will be de-ener­gized and the system is
locked out until the power is
cycled or the alarm is reset
through the keypad.

Alarm will be generated.

Alarm will be generated.

Alarm will be generated.

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3-2

Table 3-2. Alarm Codes (Continued)

ALARM

NO

25 Motor Failure A motor has not reached

26 Not used
31 Maintenance Alarm 1 The compressor hour

32 Maintenance Alarm 2 The evaporator hour

99 AlarmQueue Full All locations of the alarm

TITLE CAUSE REMEDY CONTROLLER

full operating speed or
the condenser motors
have shut down due to a
pressure alarm or the
motor fuse has blown.

meter is greater than the
value in Maintenance
Hour Meter 1.

meter is greater than the
value in Maintenance
Hour Meter 2.

queue are currently full
and no more alarms can
be saved.

Replace motor, or cor­rect pressure shutdown.

Reset the maintenance
hour meter.

Reset the maintenance
hour meter.

Record and clear alarm
queue.

RESPONSE

Alarm displayed and the
motor fail output is ener­gized.

Alarm will be generated.

Alarm will be generated.

Alarm will be generated.

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3-3

Table 3-3. General System Troubleshooting Procedures

INDICATION/

TROUBLE

POSSIBLE CAUSES

REFERENCE

SECTION

SYSTEM WILL NOT COOL

Compressor willnotrun Active system alarm

V-Belt loose or defective
Clutch coil defective
Clutch malfunction
Compressor malfunction

Electrical malfunction Coach power source defective

Circuit Breaker/safety device open

3.2

Check
Check/Replace
Check/Replace

See Note

Check/Repair

Check/Reset

SYSTEM RUNS BUT HAS INSUFFICIENT 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 refrigerantcharge
Service valves partially closed
Safety device open
Liquid solenoid valve stuck closed

Check

See Note.
see below

3.5.6
p. 3-5 and 4.11
p. 3-5 and 4.11

4.5 and 4.7
Open

1.6

Check
Restricted air flow No evaporator air flow or restriction p. 3-5
Heating system Heat valve stuck open p. 3-5

ABNORMAL PRESSURES

High dischargepressure Discharge transducer failure

Refrigerant overcharge
Noncondensable in system
Condenser motor failure
Condenser coil dirty

Low discharge pressure Discharge transducer failure

Compressorvalve(s)wornorbroken

Replace

4.4
Check
Check

Clean

See Note.

4.5 & 4.7

Low refrigerantcharge
High suction pressure Compressorvalve(s)wornorbroken See Note.
Low suction pressure Suction service valve partially closed

Filter-drier inlet valve partially closed

Filter-drier partially plugged

Low refrigerantcharge

Expansion valve malfunction

Restricted air flow

Suction transducer failure
Suction and dischargepressures

Compressor valve defective See Note.

Open

Check/ Open

4.10

4.5 and 4.7
p. 3-5
p. 3-5

Replace

tend to equalize when system is
operating

ABNORMAL NOISE 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

Check/Tighten

See Note.
See Note.

p. 3-5

4.12.2
Check

Check/Adjust

Clean

T-283

3-4

Table 3-3. General System Troubleshooting Procedures - Continued

INDICATION/

TROUBLE

POSSIBLE CAUSES

REFERENCE

SECTION

ABNORMAL NOISE OR VIBRATIONS --- Continued

Condenserorevaporatorfans Loose mounting hardware

Defective bearings
Blade interference
Blade missing or broken

Check/Tighten

Replace

Check

Check/Replace

CONTROL SYSTEM MALFUNCTION

Will not control Sensor or transducer defective

Relay(s) defective
Microprocessor controller malfunction

4.14 or 4.15
Check
Check

NO EVAPORATOR 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(s) defective

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

Defrost coil

Clean

Clean/Replace

Repair/Replace

Replace
Repair/Replace
Repair/Replace

Clean/Replace

Clean/Defrost

Check/Replace

1.6

Check

EXPANSION VALVE MALFUNCTION

Low suction pressure with high
superheat

Low superheatandliquid slugging
in the compressor

Side to side temperature differ­ence (Warm Coil)

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

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

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

4.5 and 4.7
Check

4.6
Replace
Replace

4.11

4.11

4.6

Check

4.6
Replace
Replace

4.11

HEATING MALFUNCTION

Insufficient heating Dirtyorpluggedheatercore

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

No Heating Coolant solenoid valve(s) malfunctioning or plugged

Controller malfunction
Pump(s) malfunctioning
Safety device open

Clean

Check/Replace

Check

Clean

Open
Repair/Replace
Repair/Replace

Check/Replace

Replace

Repair/Replace

1.6

Continuous Heating Coolant solenoid valve stuck open Replace

T-283

3-5

SECTION 4

OPERATIONREFERENC

E

SERVICE

!

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

4.1 MAINTENANCE SCHEDULE
SYSTEM

ON OFF

a. Daily Maintenance

X

b. Weekly Inspection

X

c. Monthly Inspection and Maintenance

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

X

X

Perform daily inspection

X

Check condenser, evaporator coils and air filters for cleanliness

X

Check refrigerant hoses and compressor shaft seal for leaks
Feel filter-drier for excessive temperature drop across drier

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

WARNING

!

REFERENCE

SECTION

2.2
None

4.1.a
None

4.5

4.10

4.1.b
None
Replace/Tighten
None
None
None

4.2 SUCTION AND DISCHARGE SERVIC E VAL VES

The suction and discharge service valves used on the
compressor are equipped with mating flanges for
connection to flanges on the compressor. These valves
are providedwith a doubleseat and a gauge connection,
whichallowsservicingof the compressorandrefrigerant
lines. (See Figure 4-1.)

Turningthe valvestemcounterclockwise (allthewayout)
will backseat the valve to open the suction or discharge
line to the compressor and close off the gauge
connection. Innormaloperation, the valve isbackseated
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)
willfrontseatthevalvetocloseoffthesuctionordischarge
line to isolate the compressor and open the gauge
connection.

To measure suction or discharge pressure, midseat the
valve byope ningthe valve clockwise1/4 to1/2 turn. With
the valve stem midway between frontseated and
backseated positions, the suction or discharge line is
open to both the compressorandthegauge connection.

To Discharge or
from Suction Line

Port to
Compressor

Service Valve
Frontseated
(clockwise)

Figure 4-1. Suction or Discharge Service Valve

4-1 T-283

Gauge
Connection

Service Valve

Backseated

(counterclockwise)

Valve Cap

Valve
Stem

4.3 INSTALLING MANIFOLD GAUGES

Themanifold gaugeset canbe usedtodeterminesystem
operatingpressures,addcharge,equalizeorevacuatethe
system. (See figure4-2.)

Low Pressure

Gauge

Hand Valve

(Open)

A. Connection to

Low Side of System

ABC

C. Connection to Either:

High Pressure

Gauge

Hand Valve

(Frontseated)

Vacuum Pump
Refrigerant Cylinder

B. Connection to

High Side of System

Oil Container
Evacuation Line

Figure 4-2. Manifold Gauge Set

The manifold gauge in figure 4-2 shows hand valves,
gaugesandrefrigerantopenings. Whenthelowpressure
hand valve is frontseated (turned all the way in), the low
(evaporator) pressure can be checked. When the high
pressure hand valve is frontseated, high (condensing)
pressure can be checked. When both valves a re open
(turned counterclockwise), high pressure vapor willflow
into the low side. When the low pressure valve is open,
the system can be charged or evacuated. Oil can also be
added to the system.

Install the manifold gauge set as follows:

a. Remove both service valve stems and service port

caps. Backseat (counterclockwise) both service
valves.

b. Connect the high side hose tightly to discharge

service valve port.

c. Connect the low side hose loosely to suction service

valve port.

d. Loosen charging (center) hose at dummy fitting of

manifold set.

e. Frontseat (clockwise) both manifold gauge hand

valves.

f. Open discharge service valve counterclockwise

approximately 1/4 to 1/2 turns.

g. Slowly open (counterclockwise) manifold discharge

hand valve approximatelyone turn.
h. Tighten charging hose onto dummy fitting.
i. Slowly open the manifold suction hand valve to

remove air from line.
j. Tightensuctionhoseatthesuctionservicevalveport.
k. Frontseat (close)both manifold hand valves.

l. Open suction service valve counterclockwise

approximately 1/4 to 1/2 turns.

4.4 PUMPING THE SYSTEM DOWN OR
REMOVING THE REFRIGERANT CHARGE

NOTE

Toavoiddamagetotheearth’sozonelayer,usea
refrigerant recoverysystemwhenever removing
refrigerant.

4.4.1 System Pumpdown

To service or replace the filter-drier, expansion valve,
evaporatorcoil,orsuctionline,pumptherefrigerantinto
condenser coil and receiver asfollows:

a. Install manifold gauge set. (Referto section4.3.)

NOTE

Thefollowingproceduremayhavetobe
repeatedseveraltimestomaintainthe1psig(6.9
kPa) pressure depending upon amount of
refrigerant absorbed in the oil.

b. Frontseat filter-drier inlet service valve by turning

clockwise. Start system and run in cooling. Stopthe
unit when the suction pressure reaches 1 psig (6.9
kPa) to maintain a slight positive pressure.

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

refrigerantinthe highsideof thesystembetweenthe
compressor suction service valve andthe filter drier
inlet valve. Thelowside ofthesystemwill nowbe at1
psig (6.9 kPa) pressure and ready for servicing,

d. Service or replace the necessary component on the

low side of the system.
e. Leak check connections. (Referto section4.5.)
f. Evacuate and dehydrate the low side. (Refer to

section4.6.)

4.4.2 Removing the Refrigerant Charge

Connect a refrigerant recovery system to the unit near
the receiver to remove refrigerant charge. Refer to
instructions provided by the manufacturer of the
refrigerant recoverysystem.

NOTES

a. Before openingupany partofthe system, a

slightpositivepressure shouldbe indicated on
the gauge.

b. 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 in the
system.

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 followingprocedure:

4-2T-283

NOTE

Itmust beemphasized thatonly the correct
refrigerant drum should be connected to
pressurizethesystem. Any other gas or
vapor willcontaminate the system, which
will requireadditionalevacuation and
evacuation of the high (discharge) side of
the system.

a. Ensure the main liquid line and driver solenoid

valves are open.

b. If system is without refrigerant, charge system with

refrigeranttobuilduppressurebetween30to50psig
(207 to 345 kPa).

c. Add sufficient nitrogen to raise system pressure to

150 to 200 psig (1.03 to 1.4 mPa).

d. Check for leaks. The recommended procedure for

finding leaks in a system is with a halide torch or
electronicleakdetector. Testingjointswithsoapsuds
is satisfactory only for locating large leaks.

e. Remove refrigerant using a refrigerant recovery

system and repair any leaks.

f. Evacuate and dehydrate the system. (Refer to

section4.6.)
g. Charge the unit. (Refer to section 4.7.)
h. Ensure that self-test has been performed and that

there are no errors or alarms indicated. (Refer to

paragraph 2-1.7.)

4.6 EVACUATION AND DEHYDRATION
a. General

Thepresenceofmoistureinarefrigerationsystemcan
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.

b. Preparation

NOTE

Using a compound gauge is not recommended

because of its inherent inaccuracy.

1. Evacuateanddehydrateonlyafterpressureleaktest.

(Refer to section 4.5.)

2. Essential tools to properly evacuate and dehydrate

any system include a good vacuum pump with a

minimumof 5 cfm (8.5 m

3

/hr)volume displacement,

CTDP/N07-00176-01),andagoodvacuumindicator

(available through Robinair Manufacturing,

Montpelier, Ohio, Part Number 14010).

3. Keepthe ambienttemperatureabove 60_F(15.6_C)

to speed evaporation of moisture. If ambient

temperature is lower than 60_F (15.6_C),icemay

formbefore moisture removalis complete.Itmay be

necessary to use heater blankets, heat lamps or

alternate sources of heat to raise system

temperature.

c. Procedure for Evacuation and

Dehydrating System

1. Remove refrigerant using a refrigerant recovery
system.

2. The recommendedmethodisconnecting three lines
(3/8”ODcoppertubingorlarger)tomanifold.
Attach one line to the filter-drier outlet valve,
compressor suction and discharge service valves.
(See Figure 4-3.)

3. Connect lines to unit and manifold and make sure
vacuumgaugevalve isclosedandvacuumpumpvalve
is open.

4. Opensolenoidvalveselectrically(jumper24vtocoil)
to ensure a good vacuum is obtained.

5. Start vacuum pump. Slowly open valveshalfway and
then open vacuum gauge valve.

6. Evacuate unit until vacuum gauge indicates 1500
microns (29.86 inches =75.8 cm)Hg vacuum. Close
gauge valve, vacuum pump valve, and stop vacuum
pump.

7. Break the vacuum with clean dry refrigerant. Use
refrigerant that the unit calls for. Raise system
pressure to approximately 2 psig (13.8 kPa).

8. Remove refrigerant using a refrigerant recovery
system.

9. Start vacuum pump and open all valves. Dehydrate
unit to 500 microns (29.90 inches = 75.9 cm) Hg
vacuum.

10. Closeoffpumpvalve,isolatevacuumgaugeinsystem
and stop pump. Wait five minutes to see if vacuum
holds.

11. Withavacuumstillin theunit,the refrigerantcharge
may be drawn into the system from a refrigerant
container on weight scales.

4.7 ADDING REFRIGERANT TO SYSTEM

4.7.1 Checking Refrigerant Charge

Thefollowingconditions mustbemettoaccuratelycheck
the refrigerant charge.

a. Coach engineoperating at high idle.
b. Unit operating in coolmode for 15 minutes.
c. Headpressureatleast150psig(1.03mPa)forR-134a

systems. (It may benecessary to block condenser
air flow to raise headpressure.)

d. Under the above conditions, the system is properly

chargedwhen therefrigerant liquidlevel is visible in
thereceiverlowersightglass.Ifitisnotvisible,addor
removerefrigerant until it is at the properlevel.

4.7.2 Adding Full Charge

a. Evacuate and dehydrate system. (Refer to section

4.6)

b. Place appropriate refrigerant cylinderonscales and

connect charging hose from container to filter-drier
inlet valve. Purge air from hoses.

4-3 T-283

c. Note weight of refrigerant and cylinder.
d. Openliquid valve onrefrigerant container. Midseat

filter-drier inlet valve and allow refrigerant to flow
intotheunit. Correctcharge willbe foundinsection

1.3.

e. When cylinder weight (scale) indicates that the

correct charge hasbeenadded,closeliquidlinevalve
on drum and backseat the filter-drierinletvalve.

4.7.3 Adding Partial Charge

4.9 CHECKING AND REPLACING HIGH
PRESSURE CUTOUT SWITC H

4.9.1 Checking High Pressure Switch

!

DO NOT USE A NITROGEN CYLINDER
WITHOUT A PRESSURE REGULATOR.
DO NOT USE OXYGEN IN OR NEAR A
REFRIGERATION SYSTEM OR AS AN
EXPL OSION MAY OCCUR.

WARNING

!

a. Start the vehicle engine and allow unit to stabilize.
b. Place appropriate refrigerant cylinderonscales and

connectcharginghose fromcontainervapor valveto
compressor suction service valve.

c. Rununitincoolmodefor15minutes.Withsuction

service valve midseated, remove air from hose at
refrigerant cylinder. Open cylinder valve and add
vapor charge until refrigerant level appears in the
lowerreceiversightglass.Undertheabove
conditions, thesystemwillbeproperlychargedwhen
the lower receiver sight glass appears full of
refrigerant. Add or remove refrigerant until the
proper level is obtained. Refrigerant level should not

appear in the upper sight glass, as this would indicate
and overcharge.

d. Backseat suction service valve. Close vapor valve on

refrigerant drum and note weight. 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.
b. Checktemperature at the condenser and receiver.
c. Check pressure at the compressor discharge service

valve.
d. Check saturation pressure as it corresponds to the

condenser/receiver temperature using the

Temperature-Pressure Chart, Table 4-4.
e. If gauge readingis 3 psig (21 kPa) or more than the

calculated P/T pressure in step d, noncondensibles

are present.
f. Remove refrigerant using a refrigerant recovery

system.
g. Evacuate and dehydrate the system. (Refer to

section4.6.)
h. Charge the unit. (Refer to section 4.7.)

a. Remove switch from unit. All units are equipped

with schrader valves at the high pressure switch
connection.

b. Connectanohmmeteracrossswitchterminals.Ifthe

switch is good, the ohmmeter will indicate no
resistance, indicating that the contacts are closed.

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

Figure 4-4.).

1

4

1. Cylinder V alve

2

3

Figure 4-3. Checking High Pressure Switch

d. Set nitrogen pressure regulator higher than cutout

point on switch being tested. (See section1.3.)

e. Opencylinder valve.Slowlyopenthe regulatorvalve

toincreasethepressureuntilitreachescutoutpoint.
The switch should open, which is indicated by an
infinite reading on an ohmmeter (no continuity).

f. Closecylindervalveandreleasepressurethroughthe

bleed-offvalve.Aspressuredropstocut-inpoint,the
switch contacts shouldclose, indicatingnoresistance
on the ohmmeter.

g. Replace switch if it does not function as outlined

above. (Refer to section 4.9.2.)

4.9.2 Repla cing High Pressure Switch

a. The high pressure switch is equippedwith schrader

valve to allow removal and installation without

pumping the unit down.
b. Disconnect wiring from defective switch.
c. Install new cutout switch.
d. Check switch operation. (Refer to section 4.9.1.)

5

6

and Gauge

2. Pressure Regulator

3. Nitrogen Cylinder

4. Pressure Gauge
(0 to 400 psig =
0to2.8mPa)

5. Bleed-Off Valve

6. 1/4 inch Connection

4-4T-283

4.10 FILTER-DRIER
a. 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.

b. To Replace Filter Drier

1. Pumpdown the unit. (Refer to section 4.4.)

2. Replacefilter-drier,ensuringthatthearrowpointsin
the direction of the refrigerant flow.

3. Drier can be evacuated at liquid service valve. (See
Figure 4-3.)

4. Check refrigerantlevel. (Refer to section 4.7.1.)

12. Run the coachforapproxi mately 30 minutes on fast
idle.

13. Check refrigerant level. (Refer to section 4.7.1.)

14. Checksuperheat. (Refer to section 4.11.b.)

1

6
7

5

4

3

2

8

9
8

4.11 THERMOSTATIC EXPANSION VALVE

The thermostat 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
responseof refrigerantflowtomatchtheevaporatorload
and (b) prevention of liquid refrigerant entering the
compressor. Unless the valve is defective, it seldom
requires any maintenance.

a. Replacingthe Expansion Valve (SeeFigure4-5.)

1. Pump down low side of the unit. (Refer to section

4.4.)

2. Remove insulation(Presstite)fromexpansion valve
bulb.

3. Loosen retainingstraps holding bulb to suction line
and detach bulbfrom the suction line.

4. Loosen flare nuts on equalizer line and disconnect
equalizer linefromthe expansion valve.

5. Remove capscrews and lift off powerheadandcage
assembliesandgaskets.

6. Check, clean and removeany foreignmaterial from
the valve body, valveseatandmating surfaces.

NOTE

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

7. Usingnew gaskets,i nstall newcage and power head
assembliesprovidedwith repair kit.

8. The thermalbulbisinstalled below the centerofthe
suctionline(fouroreighto’clockposition).Thisarea
must be clean to ensure positive bulbcontact. Strap
thermal bulb to suction line and insulate both with
“Presstite.” Ensure that retaining straps are tight.
(See Figure 4-6.)

9. Fasten equalizer line to the expansion valve.

10. Evacuate and dehydrate. (Refer to section 4-6.)

11. Openfilter-drierinletvalve(liquidlineservicevalve)
and all service valves.

10

11

1. Power Head Assembly 7. Bulb

2. Cap Seal 8 Gasket

3. Flare Seal 9. Cage Assembly

4. Retaining Nut 10. Body Flange

5. Adjusting Stem 11. Capscrew

6. Equalizer Connection

Figure 4-4. Thermostatic Expansion Valve

3

2

1

1. Suction Line (end view)

2. TXV Bulb Clamp

3. Nut and Bolt (clamp)

4. Thermocouple

5.TXVBulb(Showninthe
4’clock position)

Figure 4-5. Thermostatic Expansion Valve

Bulb and Thermocouple

Monitor the superheat over a five minute period and
record the maximum and minimum readings. Add the
maximum and minimum readings and divide by two to
determine the superheat. Thesuperheatshould be10F
to 12F.

b. To Check/Measure Superheat

NOTE

Allreadingsmust betaken fromthe suctionside
areaofthe evaporator nearthe TXV andoutof
the direct air stream.

1. Remove filter access door.

2. Remove Presstite insulation from expansion valve
bulb and suction line.

4

5

4-5 T-283

3. Loosen one TXV bulb clamp and make sure area
under clamp is clean.

4. Place temperaturethermocouplein contact with the
suction tube and parallel to the TXV bulb,andthen
secure loosened clamp making sure both bulbs are
firmly secured to suction line. (See Figure 4-5).
Reinstall insulation around the bulb.

5. Reinstall evaporator access door being careful to
route thermocouple sensing wire outside the
evaporator.

6. Connect an accurate lowpressure gauge to the 1/4”
portonthesuctionservicevalveorinstalla manifold
gauge set. (Refer to section 4.3.)

7. Startbusandrunonfastidleuntilunithasstabilized,
about20to30minutes.

NOTE

When conducting this test, the suction pressure
must be at least 6 psig (41 kPa) below the
expansion valve maximum operating pressure
(MOP). Refer to section 1.3 forMOP.

8. Fromthetemperature/pressurechart, determinethe
saturation temperature corresponding to the
evaporator outlet pressure.(SeeTable 4-4.) Addan
estimatedsuction lineloss of2psig (13.8 kPa) to the
number taken at the compressor.

9. Note the temperature of the suction gas at the
expansion valve bulb. Subtract the saturation
temperature determined i n step 8 from the
temperaturemeasuredin thisstep. Thedifference is
the superheat of the suction gas.

10. Monitorthe superheatoverafiveminute periodand
record the maximum and minimum readings. Add
themaximumandminimumreadingsanddivide by2
to determine superheat. The superheat should be
10Fto12F.

c. To Adjust Superheat

NOTE

It is not recommended to adjust thermal
expansion valves unless absolutely necessary.
The procedure is very time consuming.
Therefore, it is highly recommended that the
expansion valve be replaced rather than
adjusting.

Ifadjustment isnecessary, performthe followingprocedure:

1. Pumpdowntheloadsideofthesystem.(Referto
section4.4.)

2. Removecapscrewsandnote relative position ofcage
assembly.(See Figure 4.5.) Lift out powerheadand
cage assemblies while maintaining position of the
cage assembly. Turn/rotate cage assembly
counterclockwise to decrease superheat setting or
clockwise to increase superheat setting. Each full
turn willchange superheat setting by 1_F (0.56_C).

3. Check, clean and removeany foreignmaterial from
the valve body, valveseatandmating surfaces.

4. Reinstall powerhead andcage assemblies usingnew
gaskets.

5. Tighten capscrews.

6. Evacuate and dehydrate. (Refer to section 4-6.)

7. Openfilter-drierinletvalve(liquidlineservicevalve)
and all service valves.

8. Runthe coach for approximately 30 minutes on fast
idle.

9. Check refrigerantlevel. (Refer to section 4.7.1.)

10. Checksuperheat setting. (Refer to section 4.11.b.)

4.12 Model 05G COMPRESSOR MAINTENANCE

4.12.1 Remo ving the Compressor

If compressor is inoperative and the unit still has
refrigerant pressure, frontseat suction and discharge
service valves to trap most of the refrigerant in the
system.

If compressor is operative, pump down the system.
(Refer to section 4.4.)

a. T u rnmain batter y discon n ec t switc h to OFF position.
b. Slowly release compressor pressure.
c. Remove bolts from suction and discharge service

valve flanges.

d. Tag and disconnect wiring to the high pressure and

low pressure cutout switch, unloadersand clutch.

e. Remove four bolts holding compressor to base
f. Attach sling or other device to the compressor and

remove compressorfrom the coachthroughthe rear
access door.

g. Remove the three socket head capscrews from both

cylinderheadsthat haveunloader valvesinstalledon
the05G compressor.Removetheunloadervalveand
bypass piston assembly, keepingthesamecapscrews
with the assembly. The original unloadervalve must
be transferred to the replacement compressor. The
plug arrangement removed from the replacementis
installed intheoriginalcompressorasaseal.Ifpiston
is stuck, it may be extracted by threading a socket
headcapscrewinto topof piston.A smallTeflonseat
ring at the bottom of the piston must be removed.

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. Customer
should retain the original unloader valves
for use on the replacement compressor.

2. The piston plug that is removed from the

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

3. Donot interchangeallen-headcapscrewsthat

mount the piston plug and unloader, they
are not inte rchangeable.

4-6T-283

4. Check oil level in service replacement
compressor. (Refer to section 1.3 and 4.12.2.)

COMPRESSOR
HEAD

GASKET

BYPASS
PISTON
PLUG

FLANGE
COVER

SPRING

capscrews

(NOT INTERCHANGEABLE
WITH CONTROL VALVE
SCREWS)

Figure 4-6. Removing Bypass Piston Plug

h. Remove the high pressure switch assembly and

install on replacement compressor after checking
switchoperation.

12

11
10

9
8

7

1. Electric Unloader
Valve

2. Suction Service
Valve Charging Port

3. Suction Service
Valve

4. Clutch

5.OilFillPlug

1
2

3
4

5

6

6. Bottom Plate

7. Oil Drain Plug

8. Oil Level Sight Glass

9. Oil Pump

10. O-ring

11. Discharge Service
Valve

12. Service Port

i. Install compressor in unit by performing steps c.

through h. in reverse. It is recommended that new
locknutsbe used when replacing compressor.Install
new gaskets on service valves and tighten bolts
uniformly.

j. Unlock and turn main battery disconnect switch to

ON position..

k. Attach two lines (with hand valves near vacuum

pump) to the suction and discharge service valves.
(Dehydrateandevacuate compressorto500microns
(29.90” Hg vacuum= 75.9 cm Hgvacuum). Turn off
valves on both lines to pump.

l. Fully backseat (opencounterclockwise) both suction

and discharge service valves.

m. Remove vacuum pump lines and install manifold

gauges.

n. Start unit and check refrigerant level.

o. Checkcompressoroillevel.(Refertosection4.12.2.)

Addorremove oil if necessary.

p. Check compressor unloader operation.

Figure 4-7. Model O5G Compressor

4.12.2 Compressor Oil Level

4.12.2.1 Checking the Compressor Oil Level

NOTE

The compressor should be fully loaded (six
cylinder operation); the unit should be fully
chargedandthecompressorcrankcaseshouldbe

warm to the touch.
a. Start the unit and allowthe system to stabilize.
b. Checkthe oilsightglassonthe compressorto ensure

that nofoamingof the oilispresent after 20minutes

ofoperation.Iftheoilisfoamingexcessivelyafter20

minutes of operation, check the refrigerant system

for flood-back of liquid refrigerant. Correct this

situationbeforeproceeding.(Referto section3.3.4.)
c. Check the level of the oil in the oil level sight glass

immediately after shutting down the compressor.

Thelowestlevelvisibleshouldbebetweenthe“Min”

and “Max” indicators on the compressor crankcase

adjacent to the sight glass. (See Figure 4-8.)

4.12.2.2 Adding Oil with Compressor in System

Twomethodsforaddingoilare:the oilpumpmethod and
closed system method.

a. Oil Pump Method

1. Onecompressoroilpumpthat maybe purchasedis a

Robinairpart no.14388.This oilpumpadaptstoone

U.S. gallon (3.785 liters) metal refrigeration oil

container and pumps 2-1/2 ounces (72.5 mliters) per

stroke when connected to the suction service valve

port.Also,thereisnoneedtoremovepumpfromcan

after each use.

4-7 T-283

2. When the compressor is in operation, the pump

Resi

O

h

check valve prevents the loss of refrigerant while
allowingservicementodevelopsufficientpressureto
overcome the operatingsuction pressure to add oil,
as necessary.

3. Backseat suction service valve and connect oil
charging hose to port. Crack open the service valve
andremoveairfromtheoilhoseattheoilpump.Add
oil as necessary.

b. Closed System Method

1. In anemergency whereanoil pump is notavailable,
oil may be drawn into the compressor through the
suction service valve.

!

EXTREMECAREMUSTBETAKENTO
ENSURE THAT THE MANIFOLD
COMMON CONNECTION REMAINS
IMMERSED IN OIL AT ALL TIMES OR
AIR AND MOISTUREWILL BE DRAWN
INTO THE SYSTEM

2. Connect the suction connection of the gauge
manifold to the compressor suction service valve
port, and immerse the common connection of the
gaugemanifoldinan opencontainerofrefrigeration
oil. Refer to section 1.3.b. for oil specifications.
Removeair fromthe lines.Closethe gaugemanifold
valve.

3. Remove air from the lines.

4. With the unit running, frontseat (counterclockwise)
the suction service valve and pull a vacuum in the
compressor crankcase. Slowly crack the suction
gauge manifold valve and oil will flow through the
suctionservice valve intothe compressor.Add oilas
necessary.

4.12.2.3 Adding Oil to Service Replacement

Compressor

Service replacement compressors may or may not be
shippedwith oil.

Ifthe replacementcompressorisshippedwithoutoil,add
oil through the suction service valve flange cavity or by
removingtheoilfillplug.(SeeFigure4-8.)

4.12.2.4 Removing Oil from the Compressor:

a. If thelowest oillevel observedinparagraph4.12.2.1,

step c., is above “Max” indication on compressor
crankcase,oil mustbe removedfromthe compressor
by performing the following procedure. If lowest oil
level visible is below “Min” indication, oil must be
added tothecompressor by following theprocedure
in section 4.12.2.2.

b. Closesuctionservicevalve(frontseat)andpumpunit

downt o 3to5 psig(21 to34kPa).Reclaimremaining
refrigerant.

CAUTION

!

NOTE

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

c. Removethe oildrainplugonthe bottomplateofthe

compressoranddrain the properamount ofoilfrom
the compressor. Replace the plug securely back into
the compressor.

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

4.13 TEMPERATURE SENSOR CHECKOUT

a. An accurate ohmmeter must be used to check

resistance values shown inTable 4-1.

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 usuallybemuchhigher orlower thanthe
value given in the Table 4-1.

c. At least one sensor lead must be disconnectedfrom

the controllerbefore any reading can be taken. Not
doing sowill resultinafalse reading. Two preferred
methodsofdetermining the actualtest temperature
at the sensorare an ice bathat 32_F (0_C) and/ora
calibrateddigitaltemperature meter.

Table 4-1. Temperature Sensor

(AT, TSC, TSD and TSR) Resistance

Temperature

_F _C

--- 20 --- 28.9 165,300

--- 10 --- 23.3 117,800
0 ---17.8 85,500

10 --- 12.2 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

4.14 SUCTION AND DISCHARGE PRESSURE
TRANSDUCER CHECKOUT

NOTE

System must be operating to check transducers.

a. With the system running use the driver display or

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

stanceIn

ms

4-8T-283

b. Useadigital volt-ohmmeter measurevoltage across

thetransducerand compare tovalues inTable4-2. A
readingwithin two percent of the values in thetable
would be considered good.

Table4-2.SuctionandDischargePressure

Transducer (SPT and DPT) Voltage

Psig Voltage Psig Voltage 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 2.406
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

4.15 Replacing Sensors and Transducers

a. Turnmainbatterydisconnectswitchto OFFposition

and lock.

b. Tag and disconnect wiring from defective sensor or

transducer.
c. Remove and replace defective sensor or transducer.
d. Connectwiringtoreplacementsensorortransducer.
e. Checkout replacement sensor or transducer. (Refer

to section 4.13, 4.14 or 4.15, as applicable.)
f. Repair or replace any defective component(s), as

required.

4.16 Controller Configuration

When a controller is replaced it must be configured to
workinthemodelofunititisbeinginstalledin.Table4-3
shows the configuration jumpersettingsthatmustbe set
to correctly operate the Capri-280 SEPTA unit.

4-9 T-283

Table 4-3. Controller Configuration

Configuration Description Jumper

A. High Reheat --- When this configuration is removed the unit will default

REMOVED
to high speed in reheat mode and in the low speed cool band. If not
removed heat reheat will default to low speed.

B. High Vent --- When this configuration is removed the unit will default to

REMOVED
high speed in vent mode. If not removed vent mode will default to
low speed.

C. NA IN
D. Reheat/Cycle --- When the reheat cycle configuration is removed the

REMOVED
unit is in reheat mode. The default configuration is cycle clutch
mode.

E. Transducers --- When the transducer configuration is removed trans-

REMOVED
ducers will assumed to be present.

F. NA IN
G. Unit Type --- SEPTA unit enabled with G in and H removed IN
H. Unit Type --- SEPTA unit enabled with G in and H removed REMOVED

I. NA NA

J. NA IN

K. Voltage - -- When this configuration is removed the voltage selection

REMOVED

will be changed from 12 to 24V DC.

L. NA REMOVED

M. NA IN

N. C/F --- When this configuration is removed the display will show

REMOVED
temperatures in F. When not removed the display will show tempera­ture in C.

O. NA IN

P. NA IN

4-10T-283

Ta bl e 4-4. R-134a Temperature - Pressure Chart

BOLD NO. = Inches Mercury Vacuum (cm Hg Vac)

Temperature

Pressure Temperature Pressure

_F _C Psig kPa Kg/cm@ Bar _F _C Psig kPa Kg/cm@ Bar

--- 40 ---40 14.6 49.4 37.08 0.49 30 ---1 26.1 180.0 1.84 1.80

--- 35 ---37 12.3 41.6 31.25 0.42 32 0 27.8 191.7 1.95 1.92

--- 30 ---34 9.7 32.8 24.64 0.33 34 1 29.6 204.1 2.08 2.04

--- 25 ---32 6.7 22.7 17.00 0.23 36 2 31.3 215.8 2.20 2.16

--- 20 ---29 3.5 11.9 8.89 0.12 38 3 33.2 228.9 2.33 2.29

--- 18 ---28 2.1 7.1 5.33 0.07 40 4 35.1 242.0 2.47 2.42

--- 16 ---27 0.6 2.0 1.52 0.02 45 7 40.1 276.5 2.82 2.76

--- 14 ---26 0.4 1.1 0.03 0.03 50 10 45.5 313.7 3.20 3.14

--- 12 ---24 1.2 8.3 0.08 0.08 55 13 51.2 353.0 3.60 3.53

--- 10 ---23 2.0 13.8 0.14 0.14 60 16 57.4 395.8 4.04 3.96

--- 8 --- 22 2.9 20.0 0.20 0.20 65 18 64.1 441.0 4.51 4.42

--- 6 --- 21 3.7 25.5 0.26 0.26 70 21 71.1 490.2 5.00 4.90

--- 4 --- 20 4.6 31.7 0.32 0.32 75 24 78.7 542.6 5.53 5.43

--- 2 --- 19 5.6 36.6 0.39 0.39 80 27 86.7 597.8 6.10 5.98
0 --- 18 6.5 44.8 0.46 0.45 85 29 95.3 657.1 6.70 6.57
2 --- 17 7.6 52.4 0.53 0.52 90 32 104.3 719.1 7.33 7.19
4 --- 16 8.6 59.3 0.60 0.59 95 35 114.0 786.0 8.01 7.86
6 --- 14 9.7 66.9 0.68 0.67 100 38 124.2 856.4 8.73 8.56
8 --- 13 10.8 74.5 0.76 0.74 105 41 135.0 930.8 9.49 9.31

10 --- 12 12.0 82.7 0.84 0.83 110 43 146.4 1009 10.29 10.09
12 --- 11 13.2 91.0 0.93 0.91 115 46 158.4 1092 11.14 10.92
14 --- 10 14.5 100.0 1.02 1.00 120 49 171.2 1180 12.04 11.80
16 --- 9 15.8 108.9 1.11 1.09 125 52 184.6 1273 12.98 12.73
18 --- 8 17.1 117.9 1.20 1.18 130 54 198.7 1370 13.97 13.70
20 --- 7 18.5 127.6 1.30 1.28 135 57 213.6 1473 15.02 14.73
22 --- 6 19.9 137.2 1.40 1.37 140 60 229.2 1580 16.11 15.80
24 --- 4 21.4 147.6 1.50 1.48 145 63 245.6 1693 17.27 16.93
26 --- 3 22.9 157.9 1.61 1.58 150 66 262.9 1813 18.48 18.13
28 --- 2 24.5 168.9 1.72 1.69 155 68 281.1 1938 19.76 19.37

4-11 T-283

SECTION 5

ELECTRICAL

Figure 5-1 INTRODUCTION

Thissectionincludes electricalwiring schematics.Theschematic shownin thissectionis for R-134a refrigerantsystems.

5-1

Figure 5-1. Electrical Wiring Schematic Diagram

Drawing No. 62-10112-00 Sheet 1 of 3

5-2

Figure 5-1. Electrical Wiring Schematic Diagram

Drawing No. 62-10112-00 Sheet 2 of 3

5-3

Figure 5-1. Electrical Wiring Schematic Diagram

Drawing No. 62-10112-00 Sheet 3 of 3

5-4

INDEX

A

A/D, 3-1
Abnormal Noise or Vibrations, 3-5
Activation, 3-1
Adding Full Charge, 4-3
Adding Oil, 4-7

Closed system method, 4-8
Adding PartialCharge, 4-4
Adding Refrigerant to System, 4-3
Adjust Superheat , 4-6
Air Conditioning Refrigerant Cycle, 1-5
Alarmclear, 3-1
Alarm Codes, 3-2
Alarm codes, 3-1
Alarm Description, 4
Alarm queue, 3-1
Alarm Queue Full, 3-3
Alternator, 1-1
Ambient temperaturesensor, 1-2
Auto Reheat Mode, 2

compressor, 1-4, 1-5
Compressor Clutch Control, 3
Compressor Oil Level, 4-7
Compressor Unloader, 3
Compressor Unloader Control, 3
Compressor will not run, 3-4
condensate drain connections, 1-3
Condenser, 1-1

coils, 1-2

Fans, 1-2
Condenser Coil, 1-2, 1-5
Condenser Fan Motor, 1-2, 1-4
Condenser Fan Overload, 3-2
Condenser Fan Speed Control, 3
Condenser Fiberglass Base, 1-2
Condenser Motor Harness, 1-2
Condenser Motor Overloads , 1-4
Condenser Motor Plate, 1-2
Condenser Top Cover Lid, 1-2
condenser tubes, 1-4
Connectors, 1-7
Control System Malfunction, 3-5

B

Boost Pump, 3
Breaker Trip Alarm, 3-2
Breakers, 1-5
Bypass Piston Plug, 4-7

C

Capacity control, 1
charging hoses, 1-4
Check/Measure Superheat , 4-5
Checking for Noncondensibles, 4-4
Checking Refrigerant Charge, 4-3
clutch, 1-4
clutch , 1-4
Coil Freeze, 3-2
Communication Failure, 3-1
Compressor, 1-1, 3-4

controller, 1
Controller Configuration, 4-9
Controller Input Sensor, 1-4
controlling compressor capacity, 1-4
cooling, 1-3
Cooling/Reheat, 3

D

Daily Maintenance, 4-1
Data Memory, 3-1
DEHYDRATION , 4-3
Diagnostic Module, 1-9
Diagnostics, 1
discharge check valve, 1-2
Discharge Line, 1-3
Discharge Pressure, 3
Discharge Pressure Transducer Failure, 3-2
discharge service valve, 1-4

Index-1 T-283

INDEX

E

electricsolenoid unloaders, 1-4
Electrical, 5-1
Electrical Control, 1-1
Electrical malfunction, 3-4
Electrical Specifications, 1-4
Electronically Commutated DC Motors, 1-7
Error Codes, 3-1

ER 5, Program Memory, 3-1
Evacuation, 4-3
Evaporator,1-1,1-2,1-3

Blower and Motor, 1-3

Blowers, 1-1

Coils, 1-3

Fan, 1-3

Motor, 1-3

Motors, 1-1
Evaporator Coil, Curbside,Evaporator, 1-3
Evaporator Coil, Roadside, 1-3
Evaporator Fan Overload, 3-2
Evaporator Fan Speed, 3

H

heat valve, 1-3
Heater Flow Cycle, 1-6
Heating, 3
heating coils, coils, 1-3
HeatingLine, 1-3
Heating Malfunction, 3-5
Heating system, 3-4
High Pressure Cutout Switch , 4-4
High Discharge Pressure, 3-2
High discharge pressure, 3-4
HighPressureSwitch,HPS,1-5
high pressure switch, 1-4
High Pressure Switch (HPS), 1-4
High Reheat, 4-10
High suction pressure, 3-4
High V ent, 4-10
High Voltage, 3-2
Hour Meters, 4
Humidity Sight Glass, 1-3

Evaporator Fan Speed Selection, 3
Evaporator Motor Harness, 1-3
Evaporator Motor Overloads, 1-4
Evaporator/HeaterBlower (Fan)Motor,1-4
evaporator/heater coil assemblies, 1-3
excessive motor temperature, 1-4
Expansion Valve, 4-5

TXV, 1-3
ExpansionValve Malfunction, 3-5

F

Filter-drier, 1-2, 1-5, 4-5
Filter-drier, 4-5
Fuses, 1-5

G

Gas Hose, 1-2
General System Troubleshooting Procedures, 3-4

I

Installing Manifold Gauges, 4-2
internal thermalprotector switch, 1-4

K

king valves, 1-2

L

LEDS, 1-7
Left F ront Grille, 1-2
LidBoltSupport,1-2,1-3
Lid Locking Screw, 1-3
Lid Screw --- Stopper, 1-3
Lid Screw Nut, 1-2
Liquid Hose, 1-2
Liquid Line, 1-3
Liquid Line SolenoidValve, 1-2
liquid line solenoid valve, 1-2
Locking Screw Gasket, 1-2, 1-3

Index-2T-283

INDEX

LogicBoard,1-3,1-8
Low discharge pressure, 3-4
Low Pressure Shutdown, 3-2
low pressure switch, 1-4
Low Pressure Switch (LPS), 1-5
Low suction pressure, 3-4
LowVoltage,3-2

M

Main Harness, 1-1
Maintenance Alarm 1, 3-3
Maintenance Alarm 2, 3-3
Maintenance Schedule, 4-1
Manifold Gauge Set, 4-2
Model 05G Compressor, 4-6
Monthly Inspection and Maintenance, 4-1
Motor Failure, 3-3

R

receiver,1-2,1-5
Receiver Tank, 1-2
Receiver Tank Support, 1-2
Refrigerant Leak C heck, 4-2
Refrigeration Charge, 1-4
Refrigeration CycleDiagram, 1-6
Refrigeration system,3-4
Reheat/Cycle, 4-10
RelayBoard,1-1,1-3,1-7
Relays, 1-7
RemovingThe Refrigerant Charge, 4-2
ReplacingSensors and Transducers, 4-9
Restricted air flow, 3-4
Return Air Filter, 1-3
Return Air Probe Failure, 3-2
Right Front Grille, 1-2
Right Rear Lateral Grille, 1-2

N

No Evaporator Air Flow Or Restricted Air Flow, 3-5

O

Oil Pump Method, 4-7

P

Parameter Codes

P2, Coil Temperature, 5
P20, Compressor Hours High, 5
P33, Kp, 6

Superheat, 5
PowerHarness, 1-1
Power Relay, 1-1
pre---tripinspection, 1
PressureSwitches,1-1,1-5
Procedurefor Evacuationand Dehydrating System ,

4-3
ProgramMemory, 3-1
Pumping The System Down, 4-2

S

Safety Devices, 1-4
Self Diagnostics, 3-1
Self-Test , 1
Service, 4-1
Service Valve, 1-2
Square Nut, 1-2, 1-3
Starting, 1
Stopping, 1
Suction and Discharge Pressure Transducer, 1-4
Suction And Discharge Service Valves, 4-1
SuctionLine, 1-3
Suction Pressure, 3
Suction Pressure Transducer, 4-8
Suction Pressure Transducer Failure, 3-2
suction service valve, 1-4, 4-1
Superheat, 4-5
System Alarms, 3-1
system operation, 1
System Parameters, 5
System Pumpdown, 4-2

Index-3 T-283

INDEX

T

Temperature --- Pressure Chart, 4-11
Temperature Sensor Checkout, 4-8
ThermalCircuit Breakers, 1-7
thermal expansionvalves, TXV, 1-3
Thermal Switches, 1-4
ThermostaticExpansion Valve, 1-4
ThermostaticExpansion Valve , 4-5
Transducers, 1-4, 4-10

Troubleshooting, 3-1

U

UV1 Relay, 3
UV2 Relay, 3

W

Weekly Inspection, 4-1

Index-4T-283