Refrigerant Pressure Sensor / Switch: Description and Operation
A/C PRESSURE SWITCHESTwo pressure sensors protect the A/C system. If the A/C low pressure falls below 145-172 kPa (21-25 psi), then the A/C low pressure switch will open.
This will disable A/C compressor operation. This switch will then close at 262-290 kPa (38-42 psi) to allow A/C operation. If the A/C high pressure exceeds 2826 kPa (410 psi), then the A/C high pressure switch will open and not allow for the PCM interpret an A/C request. This switch will close at 2413 kPa (350 psi).
A/C REFRIGERANT PRESSURE SENSOR
The A/C refrigerant pressure sensor is a 3-wire piezoelectric pressure transducer. A 5-volt reference, low reference, and signal circuits enable the sensor to operate.
The A/C pressure signal can be between 0-5 volts. When the A/C refrigerant pressure is low, the signal value is near 0 volts. When the A/C refrigerant pressure is high, the signal value is near 5 volts. The PCM converts the voltage signal to a pressure value.
The A/C refrigerant pressure sensor protects the A/C system from operating when an excessively high or low pressure condition exists. The PCM disables the compressor clutch when the A/C pressure is more than 2826 kPa (410 psi). The clutch will be enabled after the pressure decreases to less than 1034-1724 kPa (150-250 psi).