Compressor Clutch Does Not Engage

HVAC COMPRESSOR CLUTCH DOES NOT ENGAGE

DIAGNOSTIC AIDS
The refrigerant temperature at the evaporator temperature sensor in the thermal expansion valve (TXV) controls cycling of the compressor clutch to prevent freezing of the evaporator core. The compressor is disabled when the temperature goes below 3°C (37°F) and vehicle speed is greater than 8 km/h (5 mph). The compressor is enabled when the temperature exceeds 4°C (40°F). The minimum cycling time OFF is 4 seconds. Refer to Sensor Resistance Table to review sensor resistance through the temperature ranges.

TEST DESCRIPTION

Step 1 - Step 8:

Step 9 - Step 19:

Step 20 - Step 31:

Step 32 - Step 39:

The numbers below refer to the step numbers on the diagnostic table.
2. The air conditioning (A/C) compressor relay output is disabled if the engine coolant temperature is above 128°C (262°F).
3. Place the mode switch in any position except OFF, and place the air temperature control switch in a cold setting. Use the bi-level mode for consistent testing of the A/C system operation.
6. The HVAC control module is inoperative if the module does not respond to any operator control requests.
21. The compressor is disabled when the evaporator temperature goes below 3°C (38°F).
29. DTC B3933 A/C evaporator temperature sensor circuit may also set to diagnose this circuit.
31. Check the connection by removing and securely reinstalling before replacement of the HVAC control is considered.