A/C Request Signal

A/C Pressure Sensor Circuit:

Purpose:
The Pressure Cycling Switch informs the ECM that A/C has been requested. This allows the ECM to process further information and activate the compressor.

Operation:
The Heater and A/C programmer and Control Head supply power to the pressure cycling switch. A/C system pressure determines the position of the switch.

The pressure cycling switch opens at 170 kPa (24.5 psi), eliminating A/C request input to the ECM resulting in a non functional A/C compressor. The pressure cycling switch closes at 324 kPa (47 psi), allowing A/C request input to the ECM.

Location:
The Pressure Cycling Switch is located on the evaporator housing, in the low side A/C line.