Refrigerant Pressure Sensor / Switch: Description and Operation

A/C Pressure Sensor Assembly:

The A/C pressure sensor provides a signal to the ECM to determine cooling fan, A/C compressor clutch and idle speed control.
A fault in the A/C pressure sensor circuit should cause a Code 66 to set and disable the A/C compressor clutch.

The A/C pressure sensor also provides low and high side protection for the system. If the A/C pressure signal exceeds 4.74 volts the clutch is disabled. If the A/C pressure sensor voltage is less than 0.62 volts the A/C compressor clutch is also disabled.