Circuit Description

The A/C system uses an A/C refrigerant pressure sensor mounted in high pressure side of A/C refrigerant system to monitor A/C refrigerant pressure. The powertrain control module (PCM)/engine control module (ECM) uses this information to turn ON engine coolant fans when A/C refrigerant pressure is high and to keep compressor disengaged when A/C refrigerant pressure is excessively high or low.

The Air Conditioning Pressure (ACP) sensor operates like other 3-wire sensors. The PCM/ECM applies a 5.0 volt reference and a sensor ground to sensor. Changes in A/C refrigerant pressure will cause ACP sensor input to PCM/ECM to vary. The PCM/ECM monitors ACP sensor signal circuit and can determine when signal is outside of possible range of sensor. When signal is out of range for a prolonged period of time. PCM/ECM will not allow A/C compressor clutch to engage. This is done to protect compressor.