Test Description

WARNING: This page is about a different car, the 2002 GMC Sierra, 2002 GMC Cab & Chassis Sierra, 2002 Chevrolet Silverado, and 2002 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The numbers below refer to the step numbers on the diagnostic table.

2) - The A/C compressor relay output is disabled if engine coolant temperature is above 121°C (250°F). The engine coolant indicator will illuminate at this temperature.
3) - These actions will enable the A/C compressor to operate.
4) - This test ensures that there is sufficient refrigerant in the A/C system The specific values come from the A/C System Performance Test in Heating, Ventilation and Air Conditioning.
5) - The HVAC control module is inoperative when the module does not respond to an operator control request.
6) - This action ensures that the powertrain control module (PCM) is getting an A/C request from the HVAC control module.
7) - If the A/C request LED does not illuminate the HVAC control assembly is not grounding the A/C request signal circuit.
8) - Since the A/C system pressure has been verified in Step 4 this step will verify the integrity of the A/C request signal circuits, if the A/C Request Signal parameter is Yes then there is a concern with the A/C high pressure switch.
10) - Since the A/C system pressure has been verified in Step 4 this step will verify the integrity of the A/C low pressure signal circuit and the ground circuit of the A/C low pressure switch, if the A/C Compressor Cycling Switch parameter is Normal then there is a concern with the A/C low pressure switch.
14) - If the test lamp remains illuminated the A/C compressor clutch relay control circuit is shorted to ground.
18) - If the fused jumper opens during this step the A/C compressor clutch supply voltage circuit is short to ground.
22) - When the blower motor is in the OFF position, a voltage is applied to the OFF blower motor control circuit. The A/C system will not operate if a voltage is applied to the OFF blower motor control circuit.
27) - Ensure that both A/C request signal circuits of the A/C high pressure switch are tested for listed conditions.

Fig 1: HVAC Compressor Clutch Does Not Engage Diagnosis (Steps 1-8)

Courtesy of GENERAL MOTORS CORP.

Fig 2: HVAC Compressor Clutch Does Not Engage Diagnosis (Steps 9-19)

Courtesy of GENERAL MOTORS CORP.

Fig 3: HVAC Compressor Clutch Does Not Engage Diagnosis (Steps 20-31)

Courtesy of GENERAL MOTORS CORP.

Fig 4: HVAC Compressor Clutch Does Not Engage Diagnosis (Steps 32-41)

Courtesy of GENERAL MOTORS CORP.