United Technologies Carrier TRANSICOLD 68RM35-604-20 Operation manual

T-288
Rearmount
68RM35-604-20
R-134a
NYCDOT

SERVICE MANUAL
OPERATION AND
BUS AIR CONDITIONING UNIT
Rearmount
68RM35-604-20
R-134a
Carrier Transicold Division, Carrier Corporation, P.O. Box 4805, Syracuse, N.Y. 13221
Carrier Corporation 1999 DPrinted in U. S. A. 0699

i
SAFETY SUMMARY
GENERAL SAFETY NOTICES
Thefollowinggeneralsafetynoticessupplementthespecificwarningsandcautionsappearingelsewhereinthismanual.
They are recommended precautions that must be understood and applied during operation and maintenance of the
equipment covered herein. The general safety notices are presented in the following three sections labeled: First Aid,
Operating Precautions and Maintenance Precautions. A listing of the specific warnings and cautions appearing
elsewhere in the manual follows the general safety notices.
FIRST AID
Aninjury, no matter howslight, should never go unattended. Alwaysobtain firstaid or medical attentionimmediately.
OPERATING PRECAUTIONS
Always wear safety glasses.
Keep hands, clothing and tools clear of the evaporator and condenser fans.
No work should be performed on the unit until all circuit breakers and start-stop switches are turned off, and power
supply is disconnected.
Always work in pairs. Never work on the equipment alone.
In case of severe vibration or unusual noise, stop the unit and investigate.
MAINTENANCE PRECAUTIONS
Beware of unannounced starting of the evaporator and condenser fans. Do not open the condenser fan grille or
evaporator access panels before turning power off, and disconnecting and securing the power plug.
Be sure power is turned off before working on motors, controllers, solenoid valves and electrical control switches. Tag
circuit breaker and power supply to prevent accidental energizing of circuit.
Donotbypassanyelectricalsafetydevices,e.g.bridginganoverload,orusinganysortofjumperwires.Problemswiththe
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).

ii
SAFETY SUMMARY
SPECIFIC WARNING AND CAUTION STATEMENTS
TohelpidentifythelabelhazardsontheUnitandexplainthelevelofawarenesseachonecarries,anexplanationisgiven
with the appropriate consequences:
DANGER --- means an immediate hazard which WILL result in severe personal injury or death.
WARNING --- means to warn against hazards or unsafe conditions which COULD result in severe personal injury or
death.
CAUTION --- meanstowarnagainstpotentialhazardorunsafepracticewhichCOULDresultinminorpersonalinjury,
product or property damage.
The statements listed below are applicable to the refrigeration unit and may appear elsewhere in this manual. These
recommended precautions must be understood and applied during operation and maintenance of the equipment covered
herein.
WARNING
When servicing the unit, use caution when handling R-134a. This refrigerant when in contact with high
temperatures (about 1000_F) will decompose into highly corrosive and toxic compounds.
WARNING
Be sure to avoid refrigerant coming in contact with the eyes. Should refrigerant come in contact with the
eyes, wash eyes for minimum of 15 minutes with potable water only. THE USE OF MINERAL OIL OR
REFRIGERANT OILS IS NOT RECOMMENDED.
WARNING
Be sure to avoid refrigerant coming in contact with the skin. Should refrigerant come in contact with the
skin, it should be treated as if the skin had been frostbitten or frozen.
WARNING
Be sure ventilation in the workspace is adequate to keep the concentration of refrigerant below 1000 parts
per million. If necessary, use portable blowers.
WARNING
Beware of rotating fan blades and unannounced starting of fans.
WARNING
Do not use a nitrogen cylinder without a pressure regulator and do not use oxygen in a refrigeration
system, as an explosion could occur.
WARNING
Never fill a refrigerant cylinder beyond its rated capacity. Cylinder may rupture due to excessive pressure
when exposed to high temperatures.
WARNING
When starting the unit, be sure that all manual refrigerant valves in the discharge line are open. Severe
damage could occur from extremely high refrigerant pressures.

iii
TABLE OF CONTENTS
Section Page
SAFETY SUMMARY i.......................................................
1 DESCRIPTION 1-1............................................................
1.1 INTRODUCTION 1-1...................................................
1.2 REFRIGERATION SYSTEM COMPONENT SPECIFICATIONS 1-5...........
1.3 ELECTRICAL SPECIFICATION 1-5......................................
1.4 SAFETY DEVICES 1-5.................................................
1.5 SYSTEM OPERATING CONTROLS AND COMPONENTS 1-7...............
1.6 MOISTURE/LIQUID INDICATOR 1-9.....................................
1.7 AIR CONDITIONING REFRIGERANT CYCLE 1-10..........................
2 OPERATION 2-1..............................................................
2.1 STARTING AND STOPPING INSTRUCTIONS 2-1.........................
2.2 PRE-TRIP INSPECTION 2-1............................................
2.3 UNIT OPERATION 2-1..................................................
2.3.1 Air Conditioning Auto/Reheat Mode of Operation 2-1...............
3 TROUBLESHOOTING 3-1.....................................................
3.1 UNIT WILL NOT COOL 3-1..............................................
3.2 SYSTEM RUNS BUT HAS INSUFFICIENT COOLING 3-1...................
3.3 ABNORMAL PRESSURES 3-1..........................................
3.4 ABNORMAL NOISES OR VIBRATIONS 3-2...............................
3.5 TEMPERATURE CONTROLLER MALFUNCTION 3-2......................
3.6 NO EVAPORATOR AIR FLOW OR RESTRICTED AIR FLOW 3-2............
3.7 EXPANSION VALVE MALFUNCTION 3-2.................................
3.8 NO OR INSUFFICIENT HEATING 3-2....................................
4 SERVICE 4-1.................................................................
4.1 MAINTENANCE SCHEDULE 4-1........................................
4.2 SUCTION AND DISCHARGE SERVICE VALVES 4-1.......................
4.3 INSTALLING MANIFOLD GAUGE SET 4-1................................
4.4 SYSTEM PUMPDOWN 4-3..............................................
4.5 REMOVING REFRIGERANT CHARGE 4-3................................
4.6 REFRIGERANT LEAK CHECK 4-4.......................................
4.7 EVACUATION AND DEHYDRATION 4-4..................................
4.8 ADDING REFRIGERANT TO SYSTEM 4-6................................
4.9 CHECKING THE REFRIGERANT CHARGE 4-6...........................
4.10 FILTER-DRIER REMOVAL 4-6..........................................

iv
TABLE OF CONTENTS (CONT’D)
Section Page
4.11 CHECKING PRESSURE SWITCHES 4-7.................................
4.12 THERMOSTATIC EXPANSION VALVE 4-8................................
4.13 REMOVING THE HEATER COIL 4-9.....................................
4.14 SERVICING THE REHEAT COOLANT VALVE 4-9.........................
4.15 REMOVING THE CONDENSER FAN MOTOR 4-10.........................
4.16 SERVICING THE EVAPORATOR FAN BLOWER MOTOR ASSEMBLY 4-10....
4.16.1 Routine Examination and Cleaning 4-10............................
4.16.2 Brush Replacement 4-11.........................................
4.17 REPLACING THE RETURN AIR FILTERS 4-11.............................
4.18 COMPRESSOR 4-11....................................................
4.18.1 Replacing the Compressor 4-11...................................
4.18.2 Checking the Compressor Oil Level 4-12...........................
4.18.3 Adding Oil to the Installed Compressor 4-12........................
4.18.4 Adding Oil to Service Replacement Compressor 4-13................
4.18.5 Removing Oil from the Compressor 4-13...........................
5 ELECTRICAL SCHEMATIC WIRING DIAGRAM 5-1....................................
5.1 INTRODUCTION 5-1......................................................
LIST OF ILLUSTRATIONS
Figure Page
1-1. Unit Assembly -- Back View 1-2..........................................
1-2. Unit Assembly -- Inside View 1-3.........................................
1-3. Electrical Control Panel 1-4..............................................
1-4. Model 05G Compressor 1-4.............................................
1-5. Air Conditioning Refrigerant Cycle 1-11....................................
2-1. Thermostat Control Sequence Auto Cool Mode with Reheat 2-2.............
2-2. Automatic Low Speed Cool/Heat Mode Operation - with Reheat 2-3..........
2-3. Automatic High Speed Cool/Heat Mode Operation - with Reheat 2-4.........
2-4. Automatic High Speed Cool Mode Operation - No Reheat 2-5...............
4-1. Suction or Discharge Service Valve 4-1...................................
4-2. R-134a Manifold Gauge Set Connections 4-2.............................
4-3. Evacuation Manifold 4-4................................................
4-4. Evacuation Set-Up 4-5..................................................
4-5. Filter Drier Removal 4-7.................................................
4-6. Checking High Pressure Switch 4-7......................................
4-7. Thermostatic Expansion Valve 4-8.......................................

v
LIST OF ILLUSTRATIONS (CONT’D)
Figure Page
4-8. Thermostatic Expansion Valve Bulb and Thermocouple 4-9.................
4-9. Condenser Fan Motor Removal 4-10......................................
4-10. Evaporator Fan Blower Assembly 4-10.....................................
4-11. Model 05G Compressor 4-12.............................................
4-12. Compressor Oil Charge Connections 4-13..................................
5-1. Electrical Schematic Diagram Legend and Symbols 5-2.....................
5-2. Electrical Schematic Diagram 5-3........................................
LIST OF TABLES
Table Page
1-1. Model Chart 1-1........................................................
1-2. Unloader Pressure Switch Settings 1-6...................................
1-3. Safety Devices 1-6.....................................................
3-1. Troubleshooting Procedures 3-1.........................................
4-1. Pressure Switch Continuity Check 4-8....................................
4-2. R-134a Temperature - Pressure Chart 4-14.................................

1-1 T-288
SECTION 1
DESCRIPTION
1.1 INTRODUCTION
This manual contains operating and electrical
Data,and serviceinstructionsforthe 68RM35bus
air conditioning system shown in Table 1-1. The
68RM35unitisa one-piecesystemconsistingofa
compressor, condenser, evaporator and electrical
control panel sections. The units are installed in
the rear A/C compartment of the bus.
These units interface with the bus driver switches
and pump to provide a complete air conditioning
system.
All control systems are powered by 24 vdc
supplied by the bus battery and alternator or
alternate source.
Operation of the 68RM35 units is controlled
automatically by the electronic thermostat, which
maintains the vehicle’s interior temperature at the
desired set point.
Table 1-1. Model Chart
Model Number Refrigerant Electronic Thermostat Description Relay Board
Configuration Fan Motors
68RM35-604-20 R-134a Adjustable Heat/Cool Reheat Wound Field

1-2
T-288
24
712 4 6
11
10
ROADSIDE
(RS)
CURBSIDE
(CS)
181922
35
12
13
23
8
14
15
16
17202125
1. Condenser Fan Motor (CM1)
2. Filter-Drier Inlet Valve
3. Filter-Drier
4. Low Ambient Thermostat (LATH)
5. Filter-Drier Outlet Valve
6. Condenser Fan Motor (CM2)
7. Receiver
8. Fusible Plug
9. Condenser Coil
10. Discharge Line Check Valve
11. Discharge Line Isolation Valve
12. Receiver Sight Glass (Upper)
13. Moisture/Liquid Indicator
14. Unloader Pressure Switch (UPS3), Upper
15. Condenser Fan Switch (CFS), Lower
16. Evaporator Fan Housing, Curbside
17. Discharge Line Connection
18. Suction Line Connection
19. Unloader Pressure Switch (UPS1), Lower
20. Unloader Pressure Switch (UPS2), Upper
21. Evaporator Fan Motor (EFM1)
22. Liquid-Suction Heat Exchanger
23. Heater Coil Assembly
24. Evaporator Fan Motor (EFM2)
25. Evaporator Fan Housing, Roadside
9
Figure 1-1. Unit Assembly - Back View

1-3 T-288
2
3
4
5
ROADSIDE
(RS)
CURBSIDE
(CS)
1. Electrical Control Panel (See Figure 1-3.)
2. Liquid Line Solenoid Valve
3. Thermostatic Expansion Valve (TXV)
4. Roadside Blower Housing
5. Air Filter
6. Evaporator Coil
7. Curbside Blower Housing
1
CDR
67
Figure 1-2. Unit Assembly -- Inside View