Test Description

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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. This step ensures that the HVAC control module is receiving an input from the A/C switch.
4. These actions will enable the A/C compressor to operate.
5. 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.
7. The A/C low pressure switch parameter is out of range when the HVAC control module interprets the signal being below 151 kPa (22 psi).
8. This action will simulate a closed switch condition. If the Pressure Cycle Switch parameter reads Low Pressure than there is a circuit condition or a condition with the HVAC control module.
11. The A/C compressor relay output from the powertrain control module (PCM) is disabled if the A/C high side system pressure is interpreted to be higher than 2958 kPa (429 psi).

Fig 1: Diagnosis Procedure HVAC Compressor Clutch Does Not Engage (Step 1 To 4)
Courtesy of GENERAL MOTORS CORP.

Fig 2: Diagnosis Procedure HVAC Compressor Clutch Does Not Engage (Step 5 To 11)
Courtesy of GENERAL MOTORS CORP.

Fig 3: Diagnosis Procedure HVAC Compressor Clutch Does Not Engage (Step 12 To 19)
Courtesy of GENERAL MOTORS CORP.

Fig 4: Diagnosis Procedure HVAC Compressor Clutch Does Not Engage (Step 20 To 30)
Courtesy of GENERAL MOTORS CORP.

Fig 5: Diagnosis Procedure HVAC Compressor Clutch Does Not Engage (Step 31 To 34)
Courtesy of GENERAL MOTORS CORP.