HVAC Compressor Controls Circuit

The Powertrain Control Module (PCM) controls the compressor clutch in response to requests from the heater and A/C programmer. When the programmer requests compressor clutch engagement, and all other enable criteria are met, the PCM will energize the control relay after a delay period. The PCM engages the clutch during crank and at engine speed below the threshold. The following elements are inputs to the PCM:
^ The heater and A/C programmer request for compressor
^ The high side refrigerant pressure switch
^ The low side refrigerant pressure switch
^ The high side temperature switch
^ The low side temperature switch
^ The ambient air temperature sensor
^ The vehicle speed
^ The Heating, Ventilation, And Air Conditioning (HVAC) system mode

The voltage source of the compressor clutch is from the 10 amp HVAC relay fuse through the clutch relay. The PCM controls the clutch relay. The programmer sends a signal to the PCM that compressor operation is possible if the following conditions exist:
^ The heater setting is not OFF.
^ The A/C control setting is not OFF.
^ The outside temperature is above 5°C (41°F).
^ No compressor disabling codes are set.