Refrigerant Pressure Sensor / Switch: Description and Operation

A/C Control Circuit:

Purpose:
The PCM monitors A/C refrigerant pressure and A/C evaporator temperature to determine if the A/C system has adequate refrigerant (R134a) charge. The PCM will disable the A/C clutch whenever A/C refrigerant charge drops below a predetermined value, to reduce the chance of compressor damage.

Operation:

A/C Pressure Sensor
A 5 volt reference is supplied to the sensor and returned to the PCM on the signal line. As A/C pressure increases or decreases, the resistance of the sensor changes and varies the amount of signal returning to the PCM.

A/C Evaporator Temperature Sensor
A 5 volt reference is supplied to the sensor and returned to the PCM on the signal line. As evaporator temperature increases or decreases, the resistance of the sensor changes and varies the amount of signal returning to the PCM.

Location:
The A/C pressure sensor is located above the right hand shock tower, forward of the A/C compressor low cut-off switch.

The A/C evaporator temperature sensor is mounted in the evaporator core.