MCC 68AC430-100 Installation and operating instructions

OPERATION/SERVICE
for
68AC430-100
REV. 01/2013
T-353 Manual
T-353
©2012 Mobile Climate Control

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©2012 Mobile Climate Control 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.................................................................

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©2012 Mobile Climate Control T-353 Rev. 01/2013
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.......................................................
LIST OF TABLES
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.........................................

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©2012 Mobile Climate Control T-353 Rev. 01/2013
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.......................

Safety--1
©2012 Mobile Climate Control T-353 Rev. 01/2013
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 work should be performed on the unit untilall start-stop switches are 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--2
©2012 Mobile Climate Control T-353 Rev. 01/2013
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. Slowly Loosen The Connecting Nuts And
AvoidContactWithExposedSkinOrEyes.
CAUTION
The AC430 Rooftop Systems has R134a service port 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.

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©2012 Mobile Climate Control T-353 Rev. 01/2013
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
furnished by 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's interior 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 X4.6M
68AC430-100-2 12 VDC BT324 No X4.6M
68AC430-100-4 12 VDC BT324 Yes X4.6M
68AC430-100-5 12 VDC BT324 No X4.6M
68AC430-100-6 12 VDC BT324 Yes X7.8M
68AC430-100-7 12 VDC BT324 No X7.8M
68AC430-100-8 * 12 VDC BT324 No X7.8M
Table 1-2 Additional Support Manuals
MANUAL NUMBER EQUIPMENT COVERED TYPE OF MANUAL
T-353PL 68AC-430-100 Service Parts List
* Denotes Special Packaging

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©2012 Mobile Climate Control T-353 Rev. 01/2013
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
Condenser Section
Figure 1-1 AC430 Rooftop Unit
1.2.2 Condensing Section
The condensing section includes the condenser
coils, two (2)fan and motor 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.
1.2.3 Evaporator Section
The evaporator section includesthe evaporator coils,
two (2) single-shafted blower/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 coils 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.

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©2012 Mobile Climate Control T-353 Rev. 01/2013
1.2.4 BT-324 Microprocessor
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
provide refrigeration as required. The compressor(s)
capacity is matched to the bus requirements. Once
interior temperature reaches the desired set point,
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 SPECIFI-
CATIONS
a. Refrigerant Charge R-134a (Approximate)
NOTE
Refrigerant charge will depend on hose
lengths and diameters; or if there is an In-
Dash 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 TM-21
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)
d. High Pressure Switch (HPS)
Normally Closed
Opens at: 360 ±10 psig (20.41 ±0.68bar)
Closes at: 280 ±10 psig (13.61 ±0.68bar)
e. Low Pressure Switch (LPS)
Normally Open
Opens at: 6 ±3psig (0.41 ±0.20 bar)
Closes at: 25 ±3psig(1.7±0.20 bar)
1.4 ELECTRICAL SPECIFICATIONS - MOTORS
a. Evaporator Blower/Motor
Evaporator Motor Brushless
12 VDC
Horsepower (kW) .375 (.28)
Full Load Amps (FLA) 20.7
Operating Speed
High(RPM)
3250
Bearing Lubrication Factory Lubricated
(additional grease not required)
b. Condenser Fan Motor
Condenser Motor Permanent Magnet
12 VDC
Horsepower (kW) 1/4 (.18)
Full Load Amps (FLA) @
13.5 VDC
14.4
Operating Speed
High(RPM) 3222
Bearing Lubrication Factory Lubricated
(additional grease not required)
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)
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.
a. Pressure Switches
High Pressure Switch (HPS)
During the air conditioning 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.

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©2012 Mobile Climate Control T-353 Rev. 01/2013
Low Pressure Switch (LPS)
The low pressure switch is installed in 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 protected against high current by
an OEM supplied circuit breaker or fuse located in
the bus battery compartment (150 Amp for 12 VDC
systems). Independent 20 Amp, 12 VDC fuses
protect each condenser motor. Independent 25
Amp, 12 VDC fuses protect each evaporator motor.
Output circuits are protected 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, thermostatic
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 tubes. The condenser fan circulates
surrounding air (which is at a temperature lower than
the refrigerant) over the outside of the condenser
tubes. Heat transfer is established from the
refrigerant (inside the tubes) to the condenser air
(flowing over the tubes). The condenser tubes have
fins designed to improve the transfer of heat from
the refrigerant gas to the air; this removal of heat
causes the refrigerant to liquefy, thus liquid
refrigerant leaves the condenser and flows to the
receiver.
The refrigerant leaves the receiver and passes
through the receiver outlet/service valve, through a
filter-drier where a desiccant keeps the refrigerant
clean and dry.
From the filter-drier, the liquid refrigerant then flows
through the liquid line to the sight-glass and then to
the thermostatic expansion valve. The thermal
expansion valve reduces pressure and temperature of
the liquid and meters the flow of liquid refrigerant to
the evaporator to obtain maximum use of the
evaporator heat transfer surface.
The low pressure, low temperature liquid that flows
into the evaporator tubes is colder than the air that is
circulated over the evaporator tubes by the
evaporator 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.

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©2012 Mobile Climate Control T-353 Rev. 01/2013
EVAPORATOR
CONDENSER
Discharge
Liquid
Suction
Coolant
1
14
13
12
11
10
9
8
6
5
4
3
2
10
11
8
77
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

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©2012 Mobile Climate Control T-353 Rev. 01/2013
1
13
23
22
21
20
19
18
17
16
15
14
121110987
6
5
4
3
2
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

2--1
©2012 Mobile Climate Control T-353 Rev. 01/2013
SECTION 2
OPERATION BT324 CONTROLLER
2.1 STARTING, STOPPING AND OPERATING INSTRUC-
TIONS
The BT324 Digital Display is marked with
international symbols (See Figure 3-1).
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.
2.1.1 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.
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 )
1
10987
6
5432
Figure 3-1 BT324 Controller
KEYS
1. Plus Key
2. Minus Key
3. Recirculate/Fresh Air Key
4. Blower Control Key
5. Automatic Climate Control (A/C)
LEDS
6. Display
7. Fresh Air Operation (Green)
8. Manual Blower Control 'ON' (Green)
9. Heating Mode (Green)
10. Malfunction Light (Red)

2--2
©2012 Mobile Climate Control T-353 Rev. 01/2013
2.3 SEQUENCE OF OPERATION BT324
2.3.1 Function of Keys when “Engine On” and controller
active:
a. Plus Key - Increases interior temperature set point
by 1°per stroke or increases manual blower speed,
depending on displayed mode.
b. Minus Key - Decreases interior temperature set
point by 1°per stroke or decreases manual blower
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 Control - Switches on 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
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.
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 or Minus keys to select different
blower steps. The blowers 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 remove 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 --”.
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) and Key 2 (minus) at the same
time until the display shows the word “Code”.

2--3
©2012 Mobile Climate Control T-353 Rev. 01/2013
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.
d. Press Key 3 (Recirculating Air/Fresh Air) 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.
g. Press Key 5 (automatic climate control) one time
to end the program.

3--1
©2012 Mobile Climate Control T-353 Rev. 01/2013
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
Check
Check/Replace
Check/Replace
See Table 1-2
Electrical malfunction Coach power source defective
Circuit Breaker/safety device open
Check/Repair
Check/Reset
3.2 System Runs But Has Insufficient Cooling
Compressor Drive-Belt loose or defective
Compressor valves defective
Check
See Table 1-2
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
3.3
3.5
3.6
4.10
4.7
Open
1.5
Restricted air flow No evaporator air flow or restriction 3.5
Heating system Heat valve stuck open 3.7
3.3 Abnormal Pressures
High discharge pressure Refrigerant overcharge
Noncondensable in system
Condenser motor failure
Condenser coil dirty
4.7.1
Check
Check
Clean
Low discharge pressure Compressorvalve(s)wornorbroken
Low refrigerant charge
See Table 1-2
4.7
High suction pressure Compressorvalve(s)wornorbroken See Table 1-2
Low suction pressure Suction service valve partially closed
Filter-drier inlet valve partially closed
Filter-drier partially plugged
Low refrigerant charge
Expansion valve malfunction
Restricted air flow
Open
Check/Open
4.10
4.7
3.6
3.5
Suction and discharge pressures tend
to equalize when system is operating
Compressor valve defective See Table 1-2
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--2
©2012 Mobile Climate Control T-353 Rev. 01/2013
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
Defrost coil
Clean
Clean/Replace
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
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 refrigerant charge
Wax, oil or dirt plugging valve orifice
Ice formation at valve seat
Power assembly failure
Loss of bulb charge
Broken capillary tube
4.7
Check
4.6
Replace
Replace
4.14
Low superheat and liquid slugging in
the compressor
Bulb is loose or not installed.
Superheat setting too low
Ice or other foreign material holding valve open
4.14
4.14
Side to side temperature difference
(Warm Coil)
Wax, oil or dirt plugging valve orifice
Ice formation at valve seat
Power assembly failure
Loss of bulb charge
Broken capillary
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.
Clean
Check/Replace
Check
Clean
Open
Repair/Replace
Repair/Replace
No Heating Coolant solenoid valve(s) malfunctioning or plugged
Controller malfunction
Pump(s) malfunctioning
Safety device open
Check/Replace
Replace
Repair/Replace
1.5
Continuous Heating Coolant solenoid valve stuck open 4.11

4--1
©2012 Mobile Climate Control T-353 Rev. 01/2013
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 disconnect switch to the off position.
NOTE
To avoid damage to the earth's ozone layer, use a refrigerant recovery system whenever removingrefrig
erant. When working with refrigerants you must comply with all local government environmental laws.
4.1 MAINTENANCE SCHEDULE
SYSTEM SYSTEM REFERENCE
SECTION
ON OFF
a. Daily Maintenance
X
X
Pre-trip Inspection - after starting
Check tension and condition of drive belts.
2.2
None
b. Weekly Inspection
X
X
X
X
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
See above
None
4.5
4.10
c. Monthly Inspection and Maintenance
X
X
X
X
X
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
See above
None
Replace/Tighten
None
None
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.
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), the suction (low) pressure can
be read. When the discharge pressure hand valve is
front seated, discharge (high) pressure can be read.

4--2
©2012 Mobile Climate Control T-353 Rev. 01/2013
When both valves are open (turned
counterclockwise), high pressure vapor will flow into
the low side. When only the low pressure valve is
open, the system can be charged or evacuated.
CAUTION
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.
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
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.
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 accessvalves (if applicable).
Remove the couplers from the in-line access
valves.
3. Install both in-line access valve caps.
OPENED
(Backseated )
HAND VALVE
CLOSED
(Frontseated)
HAND VALVE
SUCTION
PRESSURE
GAUGE
DISCHARGE
PRESSURE
GAUGE
To Low Side
Access Valve To High Side
Access Valve
Red Knob
Blue Knob
4. 3.
YELLOW
2.
4.
5.
6.
3.
RED
3.
BLUE
2.
1.
To Refrigerant Tank
or Vacuum Pump
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

4--3
©2012 Mobile Climate Control T-353 Rev. 01/2013
4.4 REMOVING THE REFRIGERANT CHARGE
NOTE
To avoid damage to the earth's ozone layer,
use a refrigerant recovery system whenever
removing refrigerant.
4.4.1 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. Connect a reclaimer to the center manifold gauge
set connection.
c. Recover refrigerant in accordance with reclaimer
manufacturers instructions.
DS
7.
2.
3.
4.
5.
6.
To Compressor
1.
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
4.5 REFRIGERANT LEAK CHECK
A refrigerant leak check should always be performed
after the system has been opened to replace or repair
a component.
To check for leaks in the refrigeration system,
perform the following procedure:
NOTE
It must be emphasized that only the correct
refrigerant should be used to pressurize the
system. Use of any other refrigerant will con
taminate the system, and require additional
evacuation.
a. Ensure filter drier service and solenoid valves(if
equipped) are open.
1. Filter drier service valves should 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 to raise system pressure to
150 to 200 psig (10.21 to 13.61 bar).
d. Check for leaks. The recommended procedure for
finding leaks in a system is with an electronic leak
detector. Testing joints with soapsuds issatisfacto
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
Using a compound gauge (manifold gauge) for
determination of vacuum level is not recom
mended because of its inherent inaccuracy.
a. Evacuate and dehydrate only after pressure leak
test. (Refer to paragraph 4.5)
b. Essential tools to properly evacuate and dehydrate
any system include a good vacuum pump with a
minimum of 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).