Symptom Related Diagnostic Procedures

System Symptoms

There are five basic symptoms associated with air conditioning fault diagnosis. The following conditions are not in order of priority.

No Cooling
- Is the electrical circuit to the compressor clutch functional?
- Is the electrical circuit to the blower motor(s) functional?
- Slack or broken compressor drive belt.
- Compressor partially or completely seized.
- Compressor shaft seal leak.
- Compressor valve or piston damage (may be indicated by small variation between HIGH & LOW side pressures relative to engine speed).
- Broken refrigerant pipe (causing total loss of refrigerant).
- Leak in system (causing total loss of refrigerant) - possible code 23.
- Blocked filter in the receiver drier.
- Evaporator sensor disconnected - possible code 13.
- Pressure switch faulty - possible code 23.

Insufficient Cooling
- Sluggish blower motor(s),
- Restricted blower inlet or outlet passage
- Blocked or partially restricted condenser matrix or fins.
- Blocked or partially restricted evaporator matrix.
- Blocked or partially restricted filter in the receiver drier.
- Blocked or partially restricted expansion valve.
- Partially collapsed flexible pipe.
- Expansion valve temperature sensor faulty (this sensor is integral with valve and is not serviceable).
- Excessive moisture in the system.
- Air in the system.
- Low refrigerant charge - possible code 23.
- Compressor clutch slipping.
- Blower flaps or distribution vents closed or partially seized - possible codes 41 or 46.
- Coolant flow valve not closed.
- Evaporator sensor incorrectly positioned


NOTE: Should a leak or low refrigerant be established as the cause of INSUFFICIENT COOLING, follow the procedures Recovery/Recycle/Recharge, this section, and observe all refrigerant and oil handling instructions.


Intermittent Cooling
- Is the electrical circuit to the compressor clutch consistent?
- Is the electrical circuit to the blower motor(s) consistent?
- Compressor clutch slipping?
- Motorized in-car aspirator or evaporator temperature sensor faulty, causing temperature variations - possible codes 11 or 13.
- Blocked or partially restricted evaporator or condenser.

Noisy System
- Loose or damaged compressor drive belt.
- Loose or damaged compressor mountings.
- Compressor oil level low, look for evidence of leakage.
- Compressor damage caused by low oil level or internal debris.
- Blower motor(s) noisy.
- Excessive refrigerant charge, witnessed by vibration and 'thumping' in the high pressure line (may be indicated by high HIGH & high LOW side pressures).
- Low refrigerant charge causing 'hissing' at the expansion valve (may be indicated by low HIGH side pressure).
- Excessive moisture in the system causing expansion valve noise.
- Air-lock in water pump*.

Insufficient Heating
- Coolant flow valve stuck in the closed position.
- Motorized in-car aspirator seized.
- Cool air by-pass damper stuck or seized - possible code 43.
- Blocked or restricted blower inlet or outlet.
- Low coolant level.
- Blower fan speed low.
- Coolant thermostat faulty or seized open.
- Water pump inoperative or blocked
- Air-lock in matrix*.


NOTE: * Please see 'Cooling System, Coolant.' for specific coolant fill/bleed procedures. Service and Repair