Compressor Clutch Does Not Engage

HVAC COMPRESSOR CLUTCH DOES NOT ENGAGE

DIAGNOSTIC AIDS
The air conditioning (A/C) compressor clutch will not engage under the following conditions:
- The A/C high side line pressure is over 2413 kPa (350 psi).
- Throttle angle is at 100 percent.
- Engine speed is more than 5,500 RPM.
- Engine coolant temperature (ECT) is more than 123°C (253°F).
- Evaporator core temperature is less than 0°C (32°F).
- The powertrain control module (PCM) minimum OFF time to engage the compressor is 7-9 seconds. The scan tool, A/C Relay Command Delay, body control module (BCM) Inputs data list, can validate this.
- The evaporator temperature sensor is normally closed. The evaporator temperature sensor opens at 0°C (32°F).

TEST DESCRIPTION

Steps 8 - 10:

Steps 11 - 22:

Steps 23 - 30:

The numbers below refer to the step numbers on the diagnostic table.
2. The A/C compressor relay output is disabled if the ECT is above 124°C (255°F). The Check Gages indicator will illuminate at this temperature and the driver information center (DIC) will display the ENG HOT message.
3. 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. If an audible click is heard when the 10-amp is installed then the answer is yes.
8. Checks the function of the thermistor of the evaporator temperature sensor. The thermistor and module side of the harness are located behind the glove box.
9. Checks the resistance of the two gray wires at the evaporator temperature sensor module behind the glove box. As the evaporator gets colder the evaporator circuit resistance goes up.
10. Checks the resistance of the two gray wires running out of the evaporator temperature sensor itself located at the evaporator core which is contained within the HVAC module or HEBA. As the evaporator gets colder the evaporator circuit resistance goes up.
16. If the off blower motor control circuit is shorted to ground, the output of the HVAC control module for an A/C request is disabled.