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).

TEST DESCRIPTION

Steps 1 - 3:

Steps 4 - 6:

Steps 7 - 10:

Steps 11 - 14:

Steps 15 - 17:

Steps 18 - 20:

Steps 21 - 25:

Steps 26 - 31:

Steps 32 - 34:

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).