Refrigerant Pressure Sensor / Switch: Description and Operation

The electronic A/C refrigerant pressure sensor is mounted to the line between the condenser and the evaporator. The output to the PCM is variable and depends on the pressure inside the line. A higher pressure will result in a higher voltage out.

The A/C refrigerant pressure sensor signal indicates high side refrigerant pressure to the PCM. The PCM uses this information to adjust the idle air control valve to compensate for the higher engine loads present with high A/C refrigerant pressures and to control the cooling fans.
The PCM also shares the A/C pressure sensor information with the HVAC controller. The HVAC controller uses the information to decide whether or not to send the A/C request signal to the PCM.
^ If a fault occurs in the A/C pressure sensor circuit, the HVAC controller removes the request for A/C and the PCM disables the A/C relay.
^ A fault in the A/C refrigerant pressure sensor signal will cause DTC P0530 to set.

The PCM constantly monitors the A/C system pressure in order to achieve the following effects:
^ Disengage the A/C clutch if the pressure is above 2700 kPa (440 psi).
^ Disengage the A/C clutch if pressure is below 285 kPa (38 psi).
^ Boost the idle air control in order to compensate for the A/C load at idle.
^ Control the cooling fan operation. Replace the pressure sensor if it fails. It is not repairable.