Compressor Clutch Does Not Engage

HVAC COMPRESSOR CLUTCH DOES NOT ENGAGE

DIAGNOSTIC AIDS
A/C compressor clutch will not engage under the following conditions:
- The A/C high side line pressure is over 2957 kPa (429 psi).
- The A/C low side line pressure is under 151 kPa (22 psi).
- Throttle angle is at 100 percent.
- Engine speed is more than 5500 RPM.
- Engine coolant temperature (ECT) is more than 121°C (250°F).
- Ambient air temperature is less than 5°C (40°F).
- Engine is idling at a low unstable RPM.

TEST DESCRIPTION

Steps 1-5:

Steps 6-12:

Steps 13-20:

Steps 21-33:

Steps 34-35:

The numbers below refer to the step numbers on the diagnostic table.
2. The A/C compressor output is disabled if the engine is idling at a low unstable RPM.
3. 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.
4. This step ensures that the HVAC control module is receiving an input from the A/C switch.
5. These actions will enable the A/C compressor to operate.
6. 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.
8. 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).
9. 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.
12. 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).