General Description

In order to improve engine operation, the A/C compressor operation is controlled by the PCM.

Operation

This system consists of a HVAC control assembly, separate A/C refrigerant high and low pressure switches, separate A/C high and low temperature sensors, a control relay, the compressor clutch and the PCM. When the HVAC control assembly is placed in the A/C mode, a request signal is sent to the PCM. The PCM will then energize the A/C clutch relay, unless abnormally high or low A/C pressure is detected by the A/C refrigerant pressure switches. The PCM also monitors the A/C low temperature sensors to cycle the A/C clutch ON and OFF. If the PCM detects an A/C evaporator temperature less than 2°C (36°F), the A/C clutch will be prohibited from being enabled. The PCM will also energize the cooling fans ON when A/C is requested. Refer to Electric Cooling Fan(s). The A/C control relay is controlled by the PCM so that the PCM can increase idle speed before turning ON the clutch or disable the clutch when high engine coolant temperature is detected or high engine RPM is detected.