Compressor Clutch Does Not Engage
HVAC Compressor DiagnosisHVAC Compressor Diagram Diesel:
HVAC Compressor Diagnosis (Part 1):
HVAC Compressor Diagnosis (Part 2):
HVAC Compressor Diagnosis (Part 3):
The PCM control of the A/C clutch improves idle quality and performance by performing the following conditions:
Delaying clutch engagement until the idle speed is increased
Releasing the clutch when the idle speed is too low
Providing additional fuel at the instant the clutch is applied
The additional fuel smooths the cycling of the compressor.
Turning the air conditioning ON supplies battery voltage through the high pressure and cycling switches to the PCM. When the PCM receives the voltage on the A/C request signal, the A/C enable relay circuit is grounded. The A/C compressor clutch then engages.
The A/C Compressor Low Cutout Switch provides a ground when the HVAC Control Module is placed in the A/C Max. position.
Diagnostic Aids
If the air conditioning system seems to be operating correctly at this time check the following:
An intermittent condition caused by one of the following:
Backed out terminals
Improper mating
Broken locks
Improperly formed or damaged terminals
Poor terminal to wire connection
Physical damage to the wiring harness
Corrosion
Moisture in the connector
Refer to Cooling Insufficient - Air Conditioning (A/C) Inoperative for an insufficient cooling condition.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
1. Checks for low refrigerant as the cause for no A/C.
3. The A/C request signal circuit consists of the HVAC control module, the A/C high pressure cutout switch and related wiring.