Intermittent Cooling

12. Compressor clutch slipping.
13. Blower flaps or distribution vents closed or partially seized.
14. Water valve not closed.
15. Evaporator sensor detached from evaporator.

Intermittent Cooling

1. Is the electrical circuit to the compressor clutch consistent?
2. Is the electrical circuit to the blower motor(s) consistent?
3. Compressor clutch slipping.
4. Faulty air distribution flap potentiometer or motor.
5. Motorised in-car aspirator or evaporator temperature sensor faulty, causing temperature variations.
6. Blocked or partially restricted evaporator or condenser.

Noisy System

1. Loose or damaged compressor drive belt.
2. Loose or damaged compressor mountings.
3. Compressor oil level low, look for evidence of leakage.
4. Compressor damage caused by low oil level or internal debris.
5. Blower(s) motor(s) noisy.
6. Excessive refrigerant charge, witnessed by vibration and ‘thumping’ in the high pressure line (may be indicated by high HIGH & high LOW side pressures).
7. Low refrigerant charge causing ‘hissing’ at the expansion valve (may be indicated by low HIGH side pressure).
8. Excessive moisture in the system causing expansion valve noise.

Note: Electrical faults may be more rapidly traced using PDU.

Insufficient Heating

1. Water valve stuck in the closed position.
2. Motorised in-car aspirator seized.
3. Blend flaps stuck or seized.
4. Blocked or restricted blower inlet or outlet.
5. Low coolant level.
6. Blower fan speed low.
7. Coolant thermostat faulty or seized open.