HVAC Compressor Clutch Does Not Engage

HVAC Compressor Clutch Does Not Engage

Diagnostic Aids
- The A/C compressor is protected from overheating by the compressor temperature switch, which is mounted at the rear of the A/C compressor. The switch is wired internally to the compressor and is not serviceable. The switch opens and disengages the compressor clutch when temperatures reach 135 °C (275 °F). The switch closes when the compressor temperature cools to 120 °C (248 °F).
- 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).

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Test Description
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) or above 275 kPa (40 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).