MCC 68AC430-100, 68AC430-100-4, 68AC430-100-2, 68AC430-100-5, 68AC430-100-6 Service Manual

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T-353 Manual

OPERATION/SERVICE

for

68AC430-100

T-353

REV. 01/2013

TABLE OF CONTENTS

SAFETY SUMMARY Safety-1...............................................................

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

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

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

1.2.1 Rooftop Unit 1-2......................................................................

1.2.2 Condensing Section 1-2.................................................................

1.2.3 Evaporator Section 1-2..................................................................

1.2.4 BT-324 Microprocessor 1-3..............................................................

1.3 REFRIGERATION SYSTEM COMPONENT SPECIFICATIONS 1-3.................

1.4 ELECTRICAL SPECIFICATIONS - MOTORS 1-3................................

1.5 SAFETY DEVICES 1-3......................................................

1.6 AIR CONDITIONING REFRIGERATION CYCLE 1-4............................

1.7 HEATING CYCLE 1-4.......................................................

OPERATION BT324 Controller 2-1.........................................................

2.1 STARTING, STOPPING AND OPERATING INSTRUCTIONS 2-1..................

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

2.1.2 Stopping 2-1..........................................................................

2.2 PRE-TRIP INSPECTION 2-1..................................................

2.3 SEQUENCE OF OPERATION BT324 2-2.......................................

2.3.1 Function of Keys when “Engine On” and controller active: 2-2...................................

2.3.2 Illuminating Indications (Display) 2-2.......................................................

2.4 OPERATING INSTRUCTIONS BT324 2-2......................................

2.4.1 Display 2-2...........................................................................

2.4.2 Interior Temperature Control 2-2..........................................................

2.4.3 Ventilation 2-2........................................................................

2.4.4 Reheat (optional) 2-2....................................................................

2.4.5 Temperature Indication 2-2..............................................................

2.5 CHANGING BETWEEN °F (FAHRENHEIT) AND °C(CELCIUS) 2-2..............

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

3.1 System Will Not Cool 3-1................................................................

3.2 System Runs But Has Insufficient Cooling 3-1................................................

3.3 Abnormal Pressures 3-1.................................................................

3.4 Abnormal Noise Or Vibrations 3-1.........................................................

3.5 No Evaporator Air Flow Or Restricted Air Flow 3-2...........................................

3.6 Expansion Valve Malfunction 3-2..........................................................

3.7 Heating Malfunction 3-2.................................................................

TABLE OF CONTENTS (Continued)

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

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

4.2 REMOVING COVER 4-1.....................................................

4.3 MANIFOLD GAUGE SET 4-1................................................

4.3.1 Installing R-134a Manifold Gauge/Hose Set 4-2..............................................

4.4 REMOVING THE REFRIGERANT CHARGE 4-3...............................

4.4.1 Removing Entire System Charge 4-3.......................................................

4.5 REFRIGERANT LEAK CHECK 4-3............................................

4.6 EVACUATION AND DEHYDRATION 4-3.....................................

4.6.1 General 4-3...........................................................................

4.6.2 Preparation 4-3........................................................................

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

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

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

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

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

4.9 CHECKING AND REPLACING HIGH OR LOWPRESSURE CUTOUT SWITCH 4-4...

4.9.1 Replacing High Or Low Pressure Switches 4-4................................................

4.9.2 Checking High Pressure Switches 4-5......................................................

4.9.3 Checking Low Pressure Switches 4-5.......................................................

4.10 FILTER-DRIER 4-5.........................................................

4.10.1 To Check Filter-Drier 4-5................................................................

4.10.2 To Replace Filter-Drier Assembly 4-5......................................................

4.11 SERVICING THE HEAT VALVE 4-6..........................................

4.11.1 Coil Replacement 4-6...................................................................

4.11.2 Internal Part Replacement 4-6............................................................

4.11.3 Replace Entire Valve 4-6................................................................

4.12 SERVICE VALVES 4-7.......................................................

4.13 REPLACINGRETURNAIRFILTERS 4-7.......................................

4.14 THERMOSTATIC EXPANSION VALVE 4-8....................................

4.14.1 Valve Replacement 4-9..................................................................

4.14.2 Superheat Measurement 4-9..............................................................

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

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

Table 1-1 68AC430 Models 1-1.........................................................

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

Table 3-1 General System Troubleshooting Procedures 3-1...................................

Table 4-1 R-134a Temperature - Pressure Chart 4-11.........................................

LIST OF TABLES

LIST OF FIGURES

Figure 1-1 AC430 Rooftop Unit 1-2....................................................

Figure 1-2 Refrigerant/Heat Flow Diagram, AC430 1-5.....................................

Figure 1-3 AC430 With BT324 Control Board 1-6.........................................

Figure 3-1 BT324 Controller 2-1......................................................

Figure 4-1 Manifold Gauge Set (R-134a) 4-2..............................................

Figure 4-2 In-Line Service Connections 4-3..............................................

Figure 4-3 Checking High Pressure Switch 4-5............................................

Figure 4-4 Filter-Drier Removal 4-5....................................................

Figure 4-5 Heat Valve 4-7............................................................

Figure 4-6 Service Valve R134a (High Side) 4-7...........................................

Figure 4-7 Return Air Grill Assembly With Air Filter Showing 4-8.............................

Figure 4-8 Diffuser and Filter Element 4-8...............................................

Figure 4-9 Filter, Diffuser and Composite Frame 4-8.......................................

Figure 4-10 Return Air Grill Assembly With Diffuser And Composite Frame Showing 4-8..........

Figure 4-11 Thermostatic Expansion Valve 4-9...........................................

Figure 4-12 Thermostatic Expansion Valve Bulb and Thermocouple 4-9........................

Figure 5-2 Evaporator Motors 5-2.....................................................

Figure 5-3 Condenser Motors 5-3.....................................................

Figure 5-4 BT324 Controls With (1) Compressor 5-4.......................................

Figure 5-5 BT324 Control Circuit 5-5...................................................

Figure 5-6 AC430 With BT324 Control 5-6..............................................

Figure 5-7 AC430 With BT324 Control (Electrical Panel 91-62105-00) 5-7.......................

Figure 5-8 AC430 With BT324 Control (Electrical Panel 91-62105-00) 5-8.......................

iii

SAFETY SUMMARY

GENERAL SAFETY NOTICES

The following general safety notices supplement the specific warnings and cautions appearing elsewhere in this manual. They are recommended precautions that must be understood and applied during operation and maintenance of the equipment covered herein. A listing of the specific warnings and cautions appearing elsewhere in the manual follows the general safety notices.

FIRST AID

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

OPERATING PRECAUTIONS

Always wear safety glasses.

Keep hands, clothing and tools clear of the evaporator and condenser fans.

No workshouldbe performedon the unituntilall start-stop switchesare placed in the OFF position, 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 unit cover before turning power off.

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

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

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

In case of electrical fire, open circuit switch and extinguish with CO2(never use water).

Safety--1

SPECIFIC WARNINGS AND CAUTIONS

WARNING

Be sure to observe warnings listed in the safety summary in the front of this manual before

performing maintenance on the hvac system

WARNING

Read the entire procedure before beginning work. Park the vehicle on a level surface, with

parking brake applied. Turn main electrical disconnect switch to the off position.

WARNING

Do Not Use A Nitrogen Cylinder Without A Pressure Regulator

WARNING

Do Not Use Oxygen In Or Near A Refrigeration System As An Explosion May Occur.

WARNING

The Filter-drier May Contain Liquid Refrigerant. S lowly Loosen The Connecting Nuts And

AvoidContactWithExposedSkinOrEyes.

CAUTION

The AC430 Rooftop Systems has R134a serviceport couplings installed on the compressor and on the unit piping.

CAUTION

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

suction pressure before disconnecting.

Safety--2

SECTION 1

DESCRIPTION

1.1 INTRODUCTION

This manual contains Operating Instructions, Service Instructions and Electrical Data for the Model 68AC430 Air Conditioning and Heating equipment furnished by Mobile Climate Control as showninTable1-1.

Model 68AC430 systems consists of a Rooftop unit containing the condensing section, the evaporator section and engine compartment mounted compressor(s). To complete the system, the air

conditioning and heating equipment interfaces with an optional drivers evaporator (dash-air), electrical cabling, refrigerant piping, engine coolant piping (for heating), duct work and other components furnishedby Mobile Climate Control and/or the bus manufacturer.

Additional support manuals are shown in Table 1-2.

Operation of the unit is controlled automatically by an electronic thermostat. The controls maintain the vehicle'sinterior temperature at the desired set point.

Table 1-1 68AC430 Models

Model Voltage Controller With Heat Dual Loop Single Loop Roof Radius

68AC430-100 12 VDC BT324 Yes X 4.6M

68AC430-100-2 12 VDC BT324 No X 4.6M

68AC430-100-4 12 VDC BT324 Yes X 4.6M

68AC430-100-5 12 VDC BT324 No X 4.6M

68AC430-100-6 12 VDC BT324 Yes X 7.8M

68AC430-100-7 12 VDC BT324 No X 7.8M

68AC430-100-8 * 12 VDC BT324 No X 7.8M

Table 1-2 Additional Support Manuals

MANUAL NUMBER EQUIPMENT COVERED TYPE OF MANUAL

T-353PL 68AC-430-100 Service Parts List

* Denotes Special Packaging

1--1

1.2 GENERAL DESCRIPTION

1.2.1 Rooftop Unit

The rooftop unit includes the condenser section and the evaporator section (See Figure 1-1).

Evaporator Section

Figure 1-1 AC430 Rooftop Unit

1.2.2 Condensing Section

The condensing section includes the condenser coils, two (2)fan and mot or assemblies, receiver, filter-drier and filter-drier service valves.

The condenser coils provide heat transfer surface for condensing refrigerant gas at a high temperature and pressure into a liquid at high temperature and pressure. The condenser fans circulate ambient air across the outside of the condenser tubes at a temperature lower than refrigerant circulating inside the tubes; this results in condensation of the refrigerant into a liquid. The receiver collects and stores liquid refrigerant. The receiver is also fitted with a pressure relief valve which protects the system from unsafe high pressure conditions. The filter-drier removes moisture and debris from the liquid refrigerant before it enters the thermostatic expansion valve in the evaporator assembly. The service valves enable isolation of the filter-drier for service.

Condenser Section

1.2.3 Evaporator Section

The evaporatorsection includesthe evaporatorcoils, two (2) single-shaftedblower/motor assemblies,two (optional) heater coil assemblies, a thermostatic expansion valve and condensate drain connections.

The evaporator coils provide heat transfer surface for transferring heat from air circulating over the outside of the coil to refrigerant circulating inside the tubes; thus providing cooling. The heating coils (if equipped) provide a heat transfer surface for transferring heat from engine coolant water circulating inside the tubes to air circulating over the outside surface of the tubes, thus providing heating. The fans circulate the air over the coils. The air filters remove dirt particles from the air before it passes over the coils. The thermostatic expansion valve meters the flow of refrigerant entering the evaporator coils. The heat valve controls the flow of engine coolant to the heating co ils upon receipt of a signal from the controller. The condensate drain connections provide a means for connecting tubing for disposing of condensate collected on the evaporator coils during cooling operation.

1--2

1.2.4 BT-324 Microprocessor

1.4 ELECTRICAL SPECIFICATIONS - MOTORS

This BT-324 controller has three (3) modes, Auto, Vent (Cycle clutch type) and Heat.

In the auto mode the compressor is energized while the evaporator and condenser fans are operated to providerefrigerationas required. The compressor(s) capacity is matched to the bus requirements. Once interior temperature reaches the desired set po int, the compressor(s) is de-energized.

In the heat mode the heat valves are opened to allow a flow of engine coolant through the heat coils located in the evaporator section. The evaporator fans operate to circulate air over the heat coils in the same manner as the cooling mode.

1.3 REFRIGERATION SYSTEM COMPONENT SPECIFICATIONS

a. Refrigerant Charge R-134a (Approximate)

NOTE

Refrigerant charge will depend on hose lengths and diameters; or if there is an InDash unit (front evaporator). The following should only be used as a guideline.

AC430 Single Loop TM-21 Compressor

11 Pounds (5 kg)

b. Compressors

Compressor

Weight, (Dry) 7.5 Lbs. (3.4 kg) Oil Charge 6.1 Oz. (180 cc) PAG

c. Thermostatic Expansion Valves:

TDEN 5.8 TR

Superheat Setting Factory Set at 12°F(±1.8°F)

6.7°C (±1°C)

TGEN 4.5

Superheat Setting Factory Set at 7.2°F(4°C)

MOP70psig(4.8bar)

TM-21

a. Evaporator Blower/Motor

Evaporator Motor

Horsepower (kW) .375 (.28)

Full Load Amps (FLA) 20.7

Operating Speed High(RPM)

Bearing Lubrication

b. Condenser Fan Motor

Condenser Motor

Horsepower (kW) 1/4 (.18)

Full Load Amps (FLA) @

13.5 VDC

Operating Speed High(RPM)

Bearing Lubrication

c. Return Air Sensor

Input Range: -40 to 176° F(-40to80°C) Output: 20K ohms at 77° F(25°C)

d. Ambient Sensor (location chosen by Installer)

Input Range: -40 to 302° F (-40 to 150°C) Output: 20K ohms at 77° F(25°C)

Opens at: 25° F(10°C) Closes at: 35° F(1.7°C)

Brushless

12 VDC

3250

Factory Lubricated

(additional grease not required)

Permanent Magnet

12 VDC

14.4

3222

Factory Lubricated

(additional grease not required)

1.5 SAFETY DEVICES

System components are protected from damage caused by unsafe operating conditions with safety devices. Safety devices with Mobile Climate Control supplied equipment include high pressure switch (HPS), low pressure switch (LPS), circuit breakers and fuses.

d. High Pressure Switch (HPS)

Opens at: 360 ±10 psig (20.41 ±0.68bar) Closes at: 280 ±10 psig (13.61 ±0.68bar)

e. Low Pressure Switch (LPS)

Opens at: 6 ±3psig (0.41 ±0.20 bar) Closes at: 25 ±3psig(1.7±0.20 bar)

Normally Closed

Normally Open

a. Pressure Switches

High Pressure Switch (HPS)

During the air co nditioning cycle, compressor clutch operation will automatically stop if the HPS switch contacts open due to an unsafe operating condition. Opening HPS contacts de-energizes the compressor clutch shutting down the compressor. The high pressure switch (HPS) is installed in the condenser section.

1--3

Low Pressure Switch (LPS)

The low pressure switch is installedin the evaporator section and opens on a pressure drop to shut down the system when a low pressure condition occurs.

b. Fuses and Circuit Breakers

The Relay Board is p ro tected against high current by an OEM supplied circuit breaker or fuse located in the bus battery compartment (150 Amp for 12 VDC systems). Independen t 20 Amp, 12 VDC fuses protect each condenser motor. Independent 25 Amp, 12 VDC fuses protect each evaporator motor. Output circuits are pro tected by additional 2,3,5 and 10 Amp fuses according to circuit loads. During a high current condition, the fuse may open.

1.6 AIR CONDITIONING REFRIGERATION CYCLE

When air conditioning (cooling) is selected by the controller, the unit operates as a vapor compression system using R-134a as a refrigerant (See Figure 1-2 refrigerant flow diagram). The main components of the system are the A/C compressor, air-cooled condenser coils, receiver, filter-drier, th ermo static expansion valve, liquid line solenoid valve (if equipped), and evaporator coils.

The compressor raises the pressure and the temperature of the refrigerant and forces it into the condenser tub es. The condenser fan circulates surrounding air (which is at atemperature lower than the refrigerant) over the outside of the condenser tubes. Heat transfer is established from the refrigerant (inside the tubes) to the condenser air (flowing over the tubes). The condenser tubes have fins designed to improve the transfer of heat from the refrigerant gas to the air; this removal of heat causes the refrigerant to liquefy, thus liquid refrigerant leaves the condenser and flows to the receiver.

The refrigerant leaves the receiver and passes through the receiver outlet/service valve, th rou gh a

filter-drier where a desiccant keeps t h e refrigerant clean and dry.

From the filter-drier, the liquidrefrigerant then flows through the liquid line to the sight-glass and then to the thermostatic expansion valve. The thermal expansion valvereduces pressure and t em p erature of the liquid and meters the flow of liquid refrigerant to the evaporator to obtain maximum use of the evaporator heat transfer surface.

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

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

1.7 HEATING CYCLE

Heating circuit (See Figure 1-2) components furnished by Mobile Climate Control include the heater cores and solenoid operated heat valves. Components furnished by the bus manufacturer may include a water temperature switch (WTS) and boost water pump.

The controller automatically controls the heat valves during the heating mode to maintain required temperatures inside the bus. Engine coolant (glycol solution) is circulated through the heating circuit by the engine and an auxiliary boost water pump. When the heat valve solenoids are energized, the valves will open to allow engine coolant to flow through the heater coils. The valves are normally closed so that if a failure occurs, the system will be able to cool.

1--4

Discharge Liquid

Suction Coolant

CONDENSER

EVAPORATOR

Figure 1-2 Refrigerant/Heat Flow Diagram, AC430

1. Thermal Expansion Valve

2. Liquid Line Sight Glass

3. Fusible Plug

4. Dash Air Liquid Line

5. Suction Line

6. Discharge Line

7. Heater Coil

8. Evaporator Coil

9. Compressor

10. Service Valve

11. Condenser Coil

12. Filter-Drier

13. Receiver

14. Receiver Liquid Level Sight Glass

1--5

121110987

Figure 1-3 AC430 With BT324 Control Board

1. X3, Connector, Controller/Driver Display

2. X11, Connector, Evaporator Blower Motors

3. X12, Connector, Condenser Fan Motors/ High Pressure Switch

4. X13, Connector, Low Pressure Switch, Fresh Air Flap

5. POS, 12VDCPower Connection

6. NEG, Ground Connection

7. CF1, Condenser Fan Relay 1

8. CF2, Condenser Fan Relay 2

9. LLSV, Liquid Line Solenoid Valve Relay

10. AC1, Condenser Fan On Relay

11. AC2, Condenser Fan On Relay

12. HTR1, Relay, Evaporator High Speed

13. HTR2, Relay, Evaporator Low Speed

14. F1, Fuse, Evaporator Motor

15. F2, Fuse, Evaporator Motor

16. F3, Fuse, Condenser Motor

17. F4, Fuse, Condenser Motor

18. F5, Fuse, LLSV

19. F6, Fuse, Condenser Fan Relay

20. F7, Fuse, Pressure Switch Relay

21. F8, Fuse, Heat Valve/ Pump Relay

22. F9, Fuse, Heat Valve/Floor Relay

23. RAS, Return Air Sensor

1--6

SECTION 2

OPERATION BT324 CONTROLLER

2.1 STARTING, STOPPING AND OPERATING INSTRUCTIONS

The BT324 Digital Display is marked with international symbols (See Figure 3-1).

2.1.1 Starting

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

b. When the 12VDC power is applied, the driver dis

play will illuminate and show return air set point. Press the A/C key (Item 5 Figure 3-1) on the dis play to trigger the start up sequence.

c. After the pre-trip inspection is completed, the

switches may be set in accordance with the desired control modes.

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

A fuse located in the battery compartment passes power for the clutch, evaporator and condenser assemblies.

2.1.2 Stopping

Toggling the A/C key (Item 5 Figure 3-1) on the display again will stop the system operation.

2.2 PRE-TRIP INSPECTION

After starting system, 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 refrigerant charge. (Refer to section 4.7.1 )

KEYS

1. Plus Key

2. Minus Key

3. Recirculate/Fresh Air Key

4. Blower Control Key

5. Automatic Climate Control (A/C)

5432

10987

Figure 3-1 BT324 Controller

LEDS

6. Display

7. Fresh Air Operation (Green)

8. Manual Blower Control 'ON' (Green)

9. Heating Mode (Green)

10. Malfunction Light (Red)

2--1

2.3 SEQUENCE OF OPERATION BT324

2.3.1 Function of Keys when “Engine On” and controller

active:

a. PlusKey - Increases interior temperature set point

by 1° per stroke or increasesmanual blower speed, depending on displayed mode.

b. Minus Key - Decreases interior temp erature set

point by 1° per stroke or decreases manual b lower speed, depending on displayed mode.

c. Recirculating Air/Fresh Air - Switches from Recir

culating Air to Fresh Air and vice-versa.

d. Blower Control - Switches on the manual blower

control.

e. Automatic Climate Con t ro l - Switches o n the Au

tomatic Temperature Control.

f. Temperature Indicator (Key2+Key3)- Shows

the inside temperature for 10 seconds. If pressed a second time shows the outside temperature for 10 seconds (optional).

g. Reheat (optional) (Key3+Key5)- Starts Reheat

mode for 3 minutes (duration adjustable).

h. Controller Off (A/C Switch To Off) -Switches

off all control functions and the display.

NOTE

The following blower steps are disabled when the automatic climate control is on: 2-, 3-step blower: Off Continuously adjustable blower: Off

2.3.2 Illuminating Indications (Display)

With “Engine-On” and Controller active

2.4 OPERATING INSTRUCTIONS BT324

When the engine is running, toggle the A/C Switch to on to activate the Air Conditioning Unit.

2.4.1 Display

The temperature can be adjusted between 64° F(18° C) and 82° F(28° C).

When the outside temperatures are below 35° F(2° C) (adjustable parameter), the cooling function remains disabled.

2.4.3 Ventilation

When the unit is operating in Automatic Climate Control mode, the blower speed is controlled based on the room temperature.

However, the blowers may be switched to manual mode of operation by pressing the blower key.

Press the Plus o r Minus keys to select different blower steps. The b lowers can not be switched OFF when Automatic Climate Control is ON.

When Automatic Climate Control is OFF, the blowers stop when the manual control is turned to zero.

2.4.4 Reheat (optional)

The Reheat mode is used to remo ve air humidity and to help defog the windshield. Press Key 3 (Recirculating Air/Fresh Air) and Key 5 (Automatic Climate Control) at the same time to activate Reheat. Heating and cooling will be energized on for 3 minutes (adjustable parameter). In addition, the blowers are switched to maximum speed and the fresh air flap is closed. At the end of the pre-set duration of time, the functions return to the previously selected settings.

Reheat mode is disabled with the outside temperature is below 35° F(2° C) (adjustable parameter), when the sensor is not installed, or when there is a sensor failure.

2.4.5 Temperature Indication

Press key 2 (minus) and key 3 (Recirculating Air/Fresh Air) at the same time to display the inside temperature for 10 seconds.

Optionally, the outside temperature may be displayed when pressing the keys a second time.

A sensor malfunction is displayed by “i --” or “o --”.

When the unit is ON, the display shows the interior set point temperature. When selecting individual functions, the display shows the corresponding information for a short period of time. The display is dark when the engine and control unit are OFF.

2.4.2 Interior Temperature Control

Press the Plus (1) or Minus (2) keys to set the desired interior temperature.

2.5 CHANGING BETWEEN °F (FAHRENHEIT) AND °C (CELCIUS )

Procedures for changing the BT324 Controller between Fahrenheit and Celsius is as follows:

a. Engine “OFF” & Ignition “ON”.

b. Press Key 1 (plus) an d Key 2 (minus) at the same

time until the display shows the word “Code”.

2--2

NOTE

After the display shows the word “Code” you have 5 seconds to enter the correct ac cess code.

c. Press Key 1 (Plus Key) one time and release.

e. Press Key 4 (blower control) one time and release.

The display will show the mode “Fah” for temperatures in °F or the mode “Cel” for temperatures in °C.

f. Press Key 1 (plus) or Key 2 (minus) to change the

temperature mode.

d. Press Key 3 (Recirculating Air/Fresh Air) one

time and release.

g. Press Key 5 (automatic climate control) one time

to end the program.

2--3

SECTION 3

TROUBLESHOOTING

Table 3-1 General System Troubleshooting Procedures

INDICATION -

TROUBLE

POSSIBLE CAUSES

REFERENCE

SECTION

3.1 System Will Not Cool

Compressor will not run Drive-Belt loose or defective

Clutch coil defective Clutch malfunction Compressor malfunction

Electrical malfunction Coach power source defective

Circuit Breaker/safety device open

Check Check/Replace Check/Replace

See Table 1-2

Check/Repair

Check/Reset

3.2 System Runs But Has Insufficient Cooling

Compressor Drive-Belt loose or defective

Compressor valves defective

Refrigeration system Abnormal pressures

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

Restricted air flow No evaporator air flow or restriction 3.5

Heating system Heat valve stuck open 3.7

Check

See Table 1-2

3.3

3.5

3.6

4.10

4.7

Open

1.5

3.3 Abnormal Pressures

High discharge pressure Refrigerant overcharge

Low discharge pressure Compressorvalve(s)wornorbroken

High suction pressure Compressorvalve(s)wornorbroken See Table 1-2

Low suction pressure Suction service valve partially closed

Suction and discharge pressures tend to equalize when system is operating

Noncondensable in system Condenser motor failure Condenser coil dirty

Low refrigerant charge

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

Compressor valve defective See Table 1-2

4.7.1 Check Check

Clean

See Table 1-2

4.7

Open

Check/Open

4.10

4.7

3.6

3.5

3.4 Abnormal Noise Or Vibrations

Compressor Loose mounting hardware

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

Check/Tighten

See Table 1-2

SeeTable 1-2

3.6

1.3 Repair/Replace Adjust/Replace

Clean

3--1

Table 3-1 General System Troubleshooting Procedures - Continued

INDICATION -

TROUBLE

POSSIBLE CAUSES

REFERENCE

SECTION

3.4 Abnormal Noise Or Vibrations - Continued

Condenser or evaporator fans Loose mounting hardware

Defective bearings Blade interference Blade missing or broken

Check/Tighten

Replace

Check

Check/Replace

3.5 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 Fan rotation incorrect

Defrost coil

Clean

Clean/Replace

Repair/Replace

Replace Repair/Replace Repair/Replace

Clean/Replace Clean/Defrost

Check/Replace

1.5

Check

3.6 Expansion Valve Malfunction

Low suction pressure with high super heat

Low superheat and liquid slugging in the compressor

Side to side temperature difference (Warm Coil)

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

Bulb is loose or not installed. 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

4.7

Check

4.6 Replace Replace

4.14

Check

4.6 Replace Replace

4.14

3.7 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

Continuous Heating Coolant solenoid valve stuck open 4.11

Clean

Check/Replace

Check

Clean

Open Repair/Replace Repair/Replace

Check/Replace

Replace

Repair/Replace

1.5

3--2

SECTION 4

SERVICE

WARNING

Be sure to observe warnings listed in the safety summary in the front of this manual before per forming maintenance on the hvac system

WARNING

Read the entire procedure before beginning work. Park the coach on a level surface, with park ing brake applied. Turn main electrical d isconnect switch to the off position.

NOTE

To avoid damage to the earth's o zone layer, use a refrigerantreco very system whenever remo ving refrig erant. When working with refrigerants you must comply with all local government environmental laws.

4.1 MAINTENANCE SCHEDULE

SYSTEM

ON OFF

a. Daily Maintenance

b. Weekly Inspection

c. Monthly Inspection and Maintenance

Pre-trip Inspection - after starting

Check tension and condition of drive belts.

Perform daily inspection

Check condenser, evaporator coils and air filters for cleanliness

Check refrigerant hoses, fittings and component connections for leaks Feel filter-drier for excessive temperature drop across drier

Perform weekly inspection and maintenance

Clean evaporator drain pans and hoses

Check wire harnesses for chafing and loose terminals

Check fan motor bearings

Check compressor mounting bolts for tightness

SYSTEM

4.2 REMOVING COVER

To remove the cover do the following:

1. Turn all the 1/4 turn cam locks counterclockwise.

2. Using two people carefully grasp the cover under the bottom edge and lift up.

REFERENCE

SECTION

2.2 None

See above None

4.5

4.10

See above None Replace/Tighten None None

4.3 MANIFOLD GAUGE SET

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

When the suction pressure hand valve is front seated (turned all the way in), th e suction (low) pressure can be read. When the discharge pressure hand valve is front seated, discharge (high) pressure can be read.

4--1

When both valves are open (turned counterclockwise),high pressure vapor willflow into the low side. When only the low pressure valve is open, the system can be charged or evacuated.

CAUTION

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

The AC430 Rooftop Systems has R134a service port couplings installed on the unit piping.

4.3.1 Installing R-134a Manifold Gauge/Hose Set

An R-134a manifold gauge/hose set with self-sealing hoses is pictured in Figure 4-1. The manifold gauge/hose set is available from Mobile Climate Control. (Mobile Climate Control P/N 07-00294-00, which includes items 1 through 6, Figure 4-1). To perform service using the manifold gauge/hose set, do the following:

a. Preparing Manifold Gauge/Hose Set for use.

1. If the manifold gauge/hose set is new or was ex

posed to the atmosphere it will need to be evacu ated to remove contaminants and air as follows:

2. Back-seat (turn counterclockwise) both field ser

vice couplers (see Figure 4-1) and mid-seat both hand valves.

3. Connect the yellow hose to a vacuum pump and

an R-134a cylinder.

CAUTION

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

2. Back-seat the low side field service coupler and front-seat both manifold set hand valves. Back seat the in-line system access valves(if applicable). Remove the coup lers from the in-line access valves.

3. Install both in-line access valve caps.

SUCTION PRESSURE GAUGE

OPENED (Backseated ) HAND VALVE

DISCHARGE PRESSURE GAUGE

CLOSED (Frontseated) HAND VALVE

4. Evacuate to 10 inches of vacuum and then charge with R134a to slightly positive pressure of 1.0 psig.

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

b. Connecting the Manifold Gauge Gauge/Hose Set.

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

1. Connect the field service couplers (see

Figure 4-1) to the high and low in-line service ports.

2. Turn the field service coupling knobs clockwise,

which will open the system to the gauge set.

3. Read the system pressures.

c. Removing the Manifold Gauge Set.

1. While the compressor is still ON, backseat (coun

terclockwise) the high side field service coupler on

To Low Side Access Valve

BLUE

Blue Knob

To Refrigerant Tank

or Vacuum Pump

YELLOW

Figure 4-1 Manifold Gauge Set (R-134a)

1. Manifold Gauge Set

2.. Hose Fitting (0.5-16 Acme)

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

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

5.. High Side Field Service Coupling

6.. Low Side Field Service Coupling

To High Side Access Valve

RED

Red Knob

4--2

4.4 REMOVING THE REFRIGERANT CHARGE

NOTE

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

NOTE

It must be emphasized that only the correct refrigerant should be used to pressurize the system. Use of any other refrigerant will con taminate the system, and require additional evacuation.

4.4.1 Removing Entire System Charge

To remove the entire refrigerant charge, do the following:

a. Connect a manifold gauge set to the system as

showninFigure4-2.

b. Con n ect a reclaimer to the center manifold gauge

set connection.

c. Recover refrigerant in accordance with reclaimer

manufacturers instructions.

To Compressor

Figure 4-2 In-Line Service Connections

1. Discharge Service Port

2. Suction Service Port

3. Manifold Gauge Set

4. Vacuum Pump

5. Reclaimer

6. Refrigerant Cylinder

7. Thermistor Vacuum Gauge

a. Ensure filter drier service and solenoid valves(if

equipped) are open.

1. Filter drier service valves shou ld be back seated.

b. If system is without refrigerant, charge system

with refrigerant vapor to build up pressure be tween 20 to 30 psig (1.36 to 2.04 bar).

c. Add sufficient nitrogen t o raise system pressure to

150 to 200 psig (10.21 to 13.61 bar).

d. Check for leaks. The recommended pro cedure for

finding leaks in a system is with an electronic leak detector. Testing joints with soapsudsissatisfacto ry only for locating large leaks.

e. Remove test gas and replace filter-drier.

f. Evacuate and dehydrate the system. (Refer to

paragraph 4.6.)

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

4.6 EVACUATION AND DEHYDRATION

4.6.1 General

The presence of moisture in a refrigeration system can have many undesirable effects. The most common are copper plating, acid sludge formation, “freezing-up” of metering devices by free water, and formation of acids, resulting in metal corrosion. An evacuation should take place after a system repair (replacement of filter drier. expansion valve, solenoid valve, etc).

4.6.2 Preparation

NOTE

Usinga compound gauge(manifold gauge) for determination of vacuum level is not recom mended because of its inherent inaccuracy.

4.5 REFRIGERANT LEAK CHECK

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

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

a. Evacuate and dehydrate only after pressure leak

test. (Refer to p aragraph 4.5)

b. Essential tools to properly evacuate and dehydrate

any system include a good vacuum pump with a minimum of 5 cfm (8.5 m3/hr) volume displace ment, (MCC P/N 07-00176-11), and a good mi cron gauge (MCC P/N 07-00414-00).

4--3

c. Keep the ambient temperature above 60°F

(15.6°C) to speed evaporation o f moisture. If am bient temperature is lower than 60°F (15.6°C),ice may form before moisture removal is complete.

f. When correct charge has been added (refer to

paragraph1.3, refrigerantspecifications), close cyl inder valve and front seat manifold discharge valve.

4.6.3 Procedure for Evacuation and Dehydrating System

a. Remove refrigerant using a refrigerant recovery

system. Refer to paragraph 4.4.1

b. The recommended method is connecting 3/8”

OD refrigerant hoses designed for vacuum service asshowninFigure5-1.

c. Make sure vacuum pump valve is open.

d. Start vacuum pump. Slowly open valves halfway

and then open vacuum gauge valve.

e. Evacuate unit until vacuum gauge indicates 500

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

f. Wait five minutes to see if vacuum holds.

g. Charge system. Refer to paragraph 4.7.2

4.7 ADDING REFRIGERANT TO SYSTEM

4.7.1 Checking Refrigerant Charge

The following conditions must be met to accurately check the refrigerant ch arge.

g. Prepare the cylinder as required to allow vapor

charging. Backseat the manifold suction valve and charge vapor until the correct charge has been added. Close cylinder valve and front seat suction manifold set.

h. Check charge level in accordance with the proce

dures of paragraph 4.7.1.

4.8 CHECKING FOR NONCONDENSIBLES

To check for non co ndensibles, proceed as follows:

a. Stabilize system to equalize pressure between the

suction and discharge side of the system.

b. Check temperature at the condenser and receiver.

c. Check pressure at the discharge (in-line) service

port.

d. Check saturation pressure as it corresponds to the

condenser/receiver temperature. See tempera ture-Pressure chart Table Table 4-1 for R134a.

a. Bus engine operating at high idle.

b. Unit operating in cool mode for 15 minutes.

c. Compressor discharge pressure at least 150 psig

(10.21 bar). (It may be necessary to block condens er air flow to raise discharge pressure.)

d. Under the above conditions, the system is proper

ly charged when the float ball in the receiver tank sight glass is showing ½ to ¾ level.

4.7.2 Adding Full Charge

a. Install manifold gauge set at the in-line suction and

discharge service ports.

b. Evacuate and dehydrate system. (Refer to para

graph 4.6)

c. Place appropriate refrigerant cylinder on scales.

Prepare to charge liquid refrigerant by connecting charging hose from container to center connec tion on gage manifold. Purge air from hoses.

d. Note weight of refrigerant and cylinder.

e. Open cylinder valve, backseat discharge valve on

gauge manifold and allow liquidrefrigerant to flow into the high side of the system

e. If gauge reading is 3 psig or more than the calcu

lated P/T pressure in step d., non-condensables are present.

f. Remove refrigerant using a refrigerant recovery

system.

g. Evacuate and dehydrate the system. (Refer to

paragraph 4.6.)

h. Charge the unit. (Refer to paragraph 4.7.2.)

4.9 CHECKING AND REPLACING HIGH OR LOWPRESSURE CUTOUT SWITCH

4.9.1 Replacing High Or Low Pressure Switches

a. The high and low pressure switches are equipped

with Schreader valves to allow removal and instal lation without recovering the refrigerant charge.

b. Disconnect wiring from defective switch.

c. Installnew cutout switch after verifying switch set

tings.

4--4

4.9.2 Checking High Pressure Switches

WARNING

Do not use a nitrogen cylinder without a pressure regulator

WARNING

Do n o t use oxygen in or near a refrigeration system as an explosion may occur.

a. Disconnect wiring and remove switch from sys

tem.

b. Connect an ohmmeter across switch terminals. If

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

c. Connect switch to a cylinder of dry nitrogen.

(SeeFigure 4-3).

point, the switch contacts should close, indicating no resistance (continuity) on the ohmmeter.

g. Replace switch if it does not function as outlined

above.

4.9.3 Checking Low Pressure Switches

a. Disconnect wiring and remove switch from sys

tem.

b. Connect an ohmmeter across switch terminals. If

the switch is good, the ohmmeter will indicate an infinite reading on an ohmmeter (no continuity).

c. Connect switch to a cylinder of dry nitrogen.

(SeeFigure 4-3).

d. Set nitrogen pressure regulator higher than switch

cutout setting. (refer to paragraph 1.3.)

e. Open cylinder valve. Slowly open the regulator

valve to increase the p ressure until it reaches cut in point. The switch should close, which is indicated by no resistance on an ohmmeter (continuity).

f. Close cylinder valve and release pressure through

the bleed-off valve. As p ressure drops to cut-out point, the switch contacts should open, indicating infinite resistance (no continuity) on the ohmme ter.

4.10 FILTER-DRIER

Figure 4-3 Checking High Pressure Switch

1. Cylinder Valve and Gauge

2. Pressure Regulator

3. Nitrogen Cylinder

4. Pressure Gauge (0 to 400 psig = 0 to 27.22 bar)

5. Bleed-Off Valve

6. 1/4 inch Connection

d. Set nitrogen pressure regulator higher than switch

cutout setting. (refer to paragraph 1.3.)

e. Open cylinder valve. Slowly open the regulator

valve to increase the pressure until it reaches cut out point. The switch should open, which is indi cated by an infinite reading on an ohmmeter (no continuity).

f. Close cylinder valve and release pressure through

the bleed-off valve. As pressure drops to cut-in

2. 3. 4.

Figure 4-4 Filter-Drier Removal

1. Filter--Drier Inlet Service Valve

2. Valve Service Port

3. Flare Nut

4. Filter--Drier

5. Liquid Line Solenoid Valve

6. Filter--Drier Outlet Service Valve

4.10.1 To Check Filter-Drier

The filter-drier (See Figure 4-4) mu st be ch anged if the system has been opened, (for any reason), or the filter drier is partially restricted. Restriction can be identified by either the outlet frosting or a temperature difference between the inlet and outlet.

4.10.2 To Replace Filter-Drier Assembly

Filter D rier replacement can be accomplished by performing the following procedure.

a. Turn the driver's A/C switch to “OFF” position. b. Front seat the filter-drier service valves on both

sides of the filter drier.

4--5

c. Connect manifold gauge set and reclaimer to the

filter drier service valve access p o rts and reclaim any refrigerant contained in the filter drier.

d. Place a new filter-drier near the unit for immediate

installation.

WARNING

The filter-drier may contain liquid refrig erant. Slowly loosen the connecting nuts and avoid contact with exposed skin or eyes.

e. Using t wo open end wrenches, slowly crack open

the connecting nuts on each side of the filter-drier assembly. Remove the filter-drier assembly.

f. Remove seal caps from the new filter-drier. Apply

a light coat of mineral oil to the filter-drier connec tions.

g. Assemble th e new filter-drierto lines ensuring that

the arrow on the body of the filter-drier points in the direction of the refrigerant flow (refrigerant flows from the receiver to the evaporator). Finger tighten the connecting nuts.

h. Tighten filter-drier connecting nuts using two

open end wrenches.

i. Connect vacuum pump to manifold gauge set and

evacuate filter to 500 microns. Close gauge valve, vacuum pump valve, and stop vacuum pump.

j. Backseat (fully close) b o th service valve ports and

replace valve caps.

k. Remove Gauges.

4.11 SERVICING THE HEAT VALVE

The heat valve (Figure 4-5) requires no maintenance unless a malfunction to the internal parts or coil occurs. This may be caused by foreign material such as: dirt, scale, or sludge in the coolant system, or improper voltage to the coil.

NOTE

The OEM supplied heating (hot water) Sole noid Valve is normally located outside of the AC430 rooftop air conditioning system.

There are only three possiblevalvemalfunctions:coil burnout, failure to open, or failure to close.

Coil burnout may be caused by the following:

1. Improper voltage

2. Continuous over-voltage, more than 10% or Un der-voltageofmorethan15%.

3. Incomplete magnetic circuit due to the omission of the coil housing or plunger.

4. Mechanical interference with movement of plung er which m ay be caused by a deformed enclosing tube.

Failure to open may be caused by the following:

1.Coil burned out or an open circuit to coil connec tions.

2. Improper voltage.

3. Torn diaphragm.

4. Defective plunger or deformed valve b o dy assem bly.

Failure to close may be caused by the following:

1. Defective plunger or deformed valve body as

sembly.

2. Foreign material in the valve.

3. Torn diaphragm.

4.11.1 Coil Replacement

a. It is not necessary to drain the coolant from the

system.

b. Place main battery disconnect switch in OFF posi

tion and lock.

c. Disconnect wire leads to coil. d. Remove coil retaining screw and nameplate. e. Lift burned-out coil from enclosing tube and re

place.

f. Connect wire leads and test operation.

4.11.2 Internal Part Replacement

a. Disconnect system from bus battery. b. Open the vent fitting at the top of the outlet head

er of the heater coil.

c. Drain coil by opening the drain-cock on the inlet

tube.

d. Disassemble valve and replace defective parts. e. Assemble valve, refill and bleed coolant lines.

4.11.3 Replace Entire Valve

a. Disconnect system from bus battery. b. Drain coolant from lines as previously described

and disconnect hoses to valve .

c. Disconnect wire leads to coil. d. Remove valve assembly from bracket. e. Install new valve and re-connect hoses. It is not

necessary to disassemble the valve when installing.

4--6

f. Refill and bleed coolant lines.

g. Connect wire leads and test operation.

10.

TO LIQUID LINE

TO FILTER/DRYER

Service Valve Frontseated (clockwise)

SERVICE PORT

Service Valve Backseated (counterclockwise)

VALVE CAP

VALVE STEM

Figure 4-5 Heat Valve

1. Coil Retaining Screw

2. Nameplate

3. Coil Housing Assembly

4. Enclosing Tube & Bonnet Assembly

5 . K i c k --- O

6. Plunger

7. Closing Spring

8. D iaphra gm

9. O ---Ring

10. Valve Body

Spring

4.12 SERVICE VALVES

The filter/drier (High Side) service valves (Figure 4-6) are provided with a double seat and a gauge port, which allows servicing of the filter drier assembly.

Turning the valvestem counterclockwise (all the way out) will backseat the valve to open the line to the system and close off the gauge port. In normal operation, the valve is backseated to allow full flow through the valve. The valve should always be backseated before removing the service port cap.

Turning the valve stem clockwise (all the way forward) will frontseat the valve to isolate the system and open the service port.

Figure 4-6 Service Valve R134a (High Side)

4.13 REPLACING RETURN AIR FILTERS

The return air filters are located behind the return air grill, inside the vehicle.

The filters shou ld be checked for cleanliness periodically depending on operating conditions. A dirty filter will restrict air flow over the evaporator coil which may cause insufficient cooling or heating and possiblefrost buildupon the coil. To remove the filters, do the following.

a. Insure air conditioning system is in the off posi

tion.

b. Remove the return air grille with the filter-diffuser

assembly, by turning the six 1/4 turn fasteners counterclockwise.

4--7

Composite Frame

Return Air Filter

Figure 4-7 Return Air Grill Assembly

With Air Filter Showing

c. Remove diffuser from the bus composite frame.

Diffuser

Air Filter

Composite Frame

Figure 4-9

Filter, Diffuser and Composite Frame

g. Place filter and diffuser into composite frame, with

filter element down (See Figure 4-9).

Return Air Filter

Figure 4-8 Diffuser and Filter Element

d. Remove and replace the filter element.

e. Center diffuser on filter element.

f. Pull filter element appro ximately 1/4 inch over

ends of the diffuser.

Captive 1/4 Fasteners

Figure 4-10 Return Air Grill Assembly

With Diffuser And Composite Frame Showing

h. Insert filter-diffuser assembly into composite

frame on bus with the six captive 1/4 fasteners. (See Figure 4-10)

i. Lock the six captive 1/4 turns in place by rotating

clockwise.

4.14 THERMOSTATIC EXPANSION VALVE

The thermostat expansion valve (Figure 4-11) is an automatic device which maintains constant superheat of the refrigerant gas leaving the

4--8

evaporator regardless of suction pressure. The valve functions are: (a) automatic control of refrigerant flow to match the evaporator load and (b) prevention of liquid refrigerant entering the compressor. Unless the valve is defective, it seldom requires any maintenance.

j. Run the coach for approximately 30 minutes on

fast idle.

k.Check refrigerant charge. (Refer to 4.7.1)

4.14.2 Superheat Measurement

NOTE

All readings must be taken from the TXV bulb location and out of the direct air stream.

Figure 4-11 Thermostatic Expansion Valve

1.. Power Head Assembly

2.. Equalizer Connection

3.. Bulb

4.14.1 Valve Replacement

a. Recover and recycle refrigerant from the sys

tem.(refer to 4.4.1)

b. Remove insulation from expansion valve bulb.

(See Figure 4-11 and Figure 4-12.)

c. Loosen retaining straps holding bulb to suction

line and detach bulb from the suction line.

d. Loosen flare nuts on equalizer line and disconnect

equalizer line from the expansion valve.

e. Check, clean and remove any foreign material

from the valve body, valve seat and mating sur faces. I f required, replace the valve.

NOTE

R-134a valves are adjustable. Valves are pre setatthefactory.

f. The thermal bulb is installed below the center of

the suction line (four or eight o'clock position). This area must be clean to ensure positive bulb contact. Strap thermal bulb to suction line. Ensure that retaining straps are tight and renew insulation.

g. Fasten equalizer line to the expansion valve.

h. Leak check the new valve (Refer to paragraph 4.5)

i. Evacuate and recharge the system. (Refer to para

graph 4.6.)

Figure 4-12 Thermostatic Expansion Valve Bulb and

Thermocouple

1.. Suction Line (section view)

2.. TXV Bulb Clamp

3.. Nut & Bolt (clamp)

4.. Thermocouple

5.. TXV Bulb (Shown in the 4’clock position)

a. Open top cover.

b. Remove Presstite insulation from expansion valve

bulb and suction line.

c. Loosen one TXV bulb clamp and make sure area

under clamp is clean.

d. Place temperature thermocouple in contact with

the suction tube and parallel to the TXV bulb, and then secure loosened clamp making sure b o t h bulb and thermocouple are firmly secured to suc tion line. (See Figure 4-12). Reinstall insulation around the bulb.

e. Connect an accurate low p ressure gauge to t h e low

pressure port.

f. Close top cover being careful to ro u te thermocou

ple sensing wire and gauge hose outside the unit.

g. Start bus and run on fast idle until unit has stabi

lized, about 20 to 30 minutes.

NOTE

When conducting this test, the suction pres sure must be at least 6 psig (0.41 bar) below the expansion valve maximum operating pressure (MOP). Refer to paragraph 1.3 for MOP.

4--9

h. From the temperature/pressure chart, determine

the saturation temperature corresponding to the evaporator outlet pressure.

i. Note the temperature of the suction gas at the ex

pansion valve bulb. Subtract the saturation tem perature from this temperature. The difference is the superheat of the suction gas.

j. The superheat may cycle from a low to high read

ing. Monitor the superheat taking readings every 3-5 minutes for a total of 5-6 readings. Calculate the superheats, add the readings and divide by the number of readings taken to determine average su perheat. The superheat should be 12 ± 1.8°F.

k. If superheat is not within tolerance, replace the

valve.

4--10

Table 4-1 R-134a Temperature - Pressure Chart

Temperature Vacuum

°F °C

“/hg cm/hg kg/cm@ bar

-40 -40 14.6 49.4 37.08 0.49

.35 .37 12.3 41.6 31.25 0.42

-30 -34 9.7 32.8 24.64 0.33

-25 -32 6.7 22.7 17.00 0.23

-20 -29 3.5 11.9 8.89 0.12

-18 -28 2.1 7.1 5.33 0.07

-16 -27 0.6 2.0 1.52 0.02

Temperature Pressure

°F °C

psig kPa kg/cm@ bar

-14 -26 0.4 1.1 0.03 0.03

-12 -24 1.2 8.3 0.08 0.08

-10 -23 2.0 13.8 0.14 0.14

-8 -22 2.9 20.0 0.20 0.20

-6 -21 3.7 25.5 0.26 0.26

-4 -20 4.6 31.7 0.32 0.32

-2 -19 5.6 36.6 0.39 0.39

0 -18 6.5 44.8 0.46 0.45

2 -17 7.6 52.4 0.53 0.52

4 -16 8.6 59.3 0.60 0.59

6 -14 9.7 66.9 0.68 0.67

8 -13 10.8 74.5 0.76 0.74

10 -12 12.0 82.7 0.84 0.83

12 -11 13.2 91.0 0.93 0.91

14 -10 14.5 100.0 1.02 1.00

16 -9 15.8 108.9 1.11 1.09

18 -8 17.1 117.9 1.20 1.18

20 -7 18.5 127.6 1.30 1.28

22 -6 19.9 137.2 1.40 1.37

24 -4 21.4 147.6 1.50 1.48

26 -3 22.9 157.9 1.61 1.58

Temperature Pressure

°F °C

psig kPa kg/cm@ bar

28 -2 24.5 168.9 1.72 1.69

30 -1 26.1 180.0 1.84 1.80

32 0 27.8 191.7 1.95 1.92

34 1 29.6 204.1 2.08 2.04

36 2 31.3 215.8 2.20 2.16

38 3 33.2 228.9 2.33 2.29

40 4 35.1 242.0 2.47 2.42

45 7 40.1 276.5 2.82 2.76

50 10 45.5 313.7 3.20 3.14

55 13 51.2 353.0 3.60 3.53

60 16 57.4 395.8 4.04 3.96

65 18 64.1 441.0 4.51 4.42

70 21 71.1 490.2 5.00 4.90

75 24 78.7 542.6 5.53 5.43

80 27 86.7 597.8 6.10 5.98

85 29 95.3 657.1 6.70 6.57

90 32 104.3 719.1 7.33 7.19

95 35 114.0 786.0 8.01 7.86

100 38 124.2 856.4 8.73 8.56

105 41 135.0 930.8 9.49 9.31

110 43 146.4 1009 10.29 10.09

115 46 158.4 1092 11.14 10.92

120 49 171.2 1180 12.04 11.80

125 52 184.6 1273 12.98 12.73

130 54 198.7 1370 13.97 13.70

135 57 213.6 1473 15.02 14.73

140 60 229.2 1580 16.11 15.80

145 63 245.6 1693 17.27 16.93

150 66 262.9 1813 18.48 18.13

155 68 281.1 1938 19.76 19.37

4--11

SECTION 5

ELECTRICAL

5.1 INTRODUCTION

conditioning units which are fitted with two (2)

double-shafted evaporator blower/motor This section includes electrical wiring schematics. The schematics shown in this section provides information for the AC430 model rooftop air

UNIT CONTROLLER FIGURE NUMBERS

68AC430 BT324 Figure 5-1 Thru Figure 5-6

68AC430 (Electrical Panel 91-62105-00) BT324 Figure 5-7 Thru Figure 5-8

assemblies and two (2) condenser fan motors.

Figure 5-2 thru Figure 5-6 shows the BT324

controller used with the AC430 system.

5--1

98--67037--00

5--2

Figure 5-2 Evaporator Motors

T-353 Rev. 01/2013

5--3

Figure 5-3 Condenser Motors

98--67037--00

T-353 Rev. 01/2013

98--67037--00

5--4

Figure 5-4 BT324 Controls With (1) Compressor

T-353 Rev. 01/2013

5--5

Figure 5-5 BT324 Control Circuit

98--67037--00

T-353 Rev. 01/2013

98--67037--00

Figure 5-6 AC430 With BT324 Control

5--6

T-353 Rev. 01/2013

Figure 5-7 AC430 With BT324 Control (Electrical Panel 91-62105-00)

INDICATES RELAY CONTACTS (NORMALLY CLOSED)

INDICATES RELAY CONTACTS (NORMALLY OPEN)

INDICATES A CONNECTOR (VARIOUS STYLES)

INDICATES A TERMINAL CONNECTION

INDICATES A WIRE GROUND

INDICATES OPTIONAL WIRING OR FEATURE

INDICATES OPTIONAL UNIT WIRING O R FEATURE

INDICATES WIRING EXTERNAL TO UNIT

INDICATES WIRING INTERNAL TO UNIT

SYMBOL DESCRIPTION

GRD

HIGHPRESSURESWITCH

FUSE,3AMP

FUSE,5AMP

A/CRELAY

ACR1--ACR2

CONDENSERFANRELAY

CFR1--CFR2

F1-- F2 FUSE,25AMP

ATS AMBIENTTEMPERATURESENSOR

DESCRIPTION

INDICATES AMBIENT TEMPERATURE SENSOR (ATS)

INDICATES FUSE WITH MANUAL RESET

INDICATES FUSE

INDICATES ELECTRICAL COMPONENT

INDICATES RELAY COIL

86 85

ATS

SYMBOL

FUSE,10AMP

HPS

F6-- F7

F8-- F9

F3-- F4 FUSE,20AMP

HTR1--HTR1 HEAT RELAY

5--7

RETURNAIRSENSOR

LOWPRESSURESWITCH

LIQUIDLINESOLENOIDVALVE

RAS

LPS

LLSV

LLSR LIQUIDLINESOLENOIDRELAY

T-353 Rev. 01/2013

POS

(+)

NEG

(--)

ATS

OPTIONAL

DIMMER

12V(+)

IGNITION

12V (+)

ALTERNATOR

12V (+)

CHASSIS GROUND

5AMP

10 AMP

GREY LOOM

BLU

2AMP

3AMP

2AMP

BRN

WHT

ACR2

HTR1

HTR2

BT--7

BT--3

BT--5

BT--1

BT--9

LLSV

X12--5

HPS

X12--6

X13--1

X3--14

BT--13

BT--18

BT--10

BT--6

BT--15

BT--11

BT324CONTROLLER

BT--14

BT--8

BT--17

BT--4

X3--15

X3--16

X3--10 (NOT USED)

DRIVERCONTROLHARNESS

X3--11

X3--9

X3--6

X3--4

X3--3

X3--2

X3--1

X3--7

X3--8 (NOT USED)BT--2

X13--3

X13--4

HTR1

ACR1

X11--5

RETURN AIR

LPS

RAS

SENSOR

M1- -PWM

X13--2

COMP CLUTCH

A B

HTR2

COOLANT

PUMP RELAY

A B

COOLANT

VALVE RELAY

A B

FRESH AIR

MOTOR

25 AMP

20 AMP

3AMP

5AMP

CFR1

CFR2

LSVR

ACR1

98--63176

X11--1

X11--3

X12--1

X12--7

5--8

M1- -1

M2- -PWM

M2- -1

M1- -A

M2- -AX12--2

LV --1

EVAP MTR 1

EVAP MTR 2

COND MTR 1

COND MTR 2

LLSV

ACR2

CFR1

CFR2

M1- -2

M2- -2

M1- -B

M2- -B

LV --1 2

X11--2

Figure 5-8 AC430 With BT324 Control (Electrical Panel 91-62105-00)

X11--4

T-353 Rev. 01/2013

INDEX

Air Filters, 4-7

Apex Unit, 1-2

Circuit Breaker, 1-4

Compressor, 1-3

Condenser Fan, 1-3

Condensing Section, 1-2

DESCRIPTION, 1-1

Maintenance Schedule, 4-1

Manifold Gauge Set, 4-2

Noncondensibles, 4-4

Operating Instructions, 2-1

OPERATION, 2-1

Pre-Trip Inspection, 2-1

Pump Down, 4-3

ELECTRICAL, 5-1

Evacuation, 4-3, 4-4

Evaporator, 1-2

Evaporator Fan, 1-3

Filter-Drier, 4-5

Fuse, 1-4

Heat Valve, 4-6

Heating Cycle, 1-4

High Pressure Switch, 1-3

Refrigerant Charge, 1-3, 4-3, 4-4

Refrigerant Removal, 4-3

Refrigeration Cycle, 1-4

SERVICE, 4-1

Starting, 2-1

Stopping, 2-1

Superheat, 4-9

Temperature Pressure Chart, 4-11

Temperature Sensor, 1-3

Thermostatic Expansion Valve, 1-3, 4-8

Low Pressure Switch, 1-3, 1-4

TROUBLESHOOTING, 3-1

Index --1

Every driver deserves the best possible

vehicle climate with MCC products

MCC provides exceptional performance in mobile climate comfort.

Specifications subject to change without notice. MCC is a registered trademark.

Member of MCC Group S Certified ISO 9001 and ISO 1 4001.

www.mcc-hvac.com

3189 Farmtrail Road York PA 17406 USA Tel: 1--800--673--2431 Fax: 1--717--764--0401

T-353 Rev. 01/2013

MCC 68AC430-100, 68AC430-100-4, 68AC430-100-2, 68AC430-100-5, 68AC430-100-6 Service Manual

Specifications and Main Features

Frequently Asked Questions

User Manual