Section 9 --- Electrical Systems - Chassis
The Executive 2005
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Blower and Motor - Just as the condenser has a fan, the evaporator has a fan called the blower.
The blower will draw air from the cab area and force the air over the evaporator coils and fins. This
forced air will ensure continuous vaporizing of the R134a.
Relays and Switches - Both electronic and vacuum switches are used in the control and operations
of the system.
Troubleshooting - The dash A/C and Heat system uses a combination of compressed air (devel-
oped by the chassis system), vacuum air (developed by the vacuum generator) and electric relays
and vacuum switches. Therefore, any repair can be classified in one of five categories:
• Electrical • Vacuum • Air Conditioner • Heater • Defroster
The following information is provided to assist in troubleshooting common operational prob-
lems which may occur:
No Heating:
1. A/C switch is turned off.
2. Blower switch is turned off.
3. Verify the proper engine coolant level.
4. Verify that the engine is reaching operating temperature.
5. Verify engine coolant is reaching water valve attached to unit.
6. Verify operation of water valve to permit engine coolant to pass through valve to heater
core.
7. Check unit fuses.
8. Check power supply to water valve and grounding.
9. Check wiring.
10. Engine thermostat faulty.
No Cooling:
1. Check that the blower is operating, A/C switch is in A/C or Max position, temperature
control is turned to Max cooling (blue area).
2. System fuses are not blown.
3. Condenser fan is operating.
4. Check power supply to unit and grounding of system.
5. Check wiring.
6. Coolant valve is leaking.
7. Drive belt is loose or broken.
8. Compressor Clutch is inoperative, will not engage.
9. Expansion Valve is faulty or frozen.
10. Thermostat control is faulty.
11. Mode control switch is faulty.
12. Compressor is faulty.
13. Loss of refrigerant.
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