Relays and Switches

A/C Pressure Sensor




An electronic A/C pressure sensor is mounted on the discharge line (high side) of the A/C compressor suction/discharge hose assembly. Its output to the PCM is variable and is dependent upon pressure inside the line. The PCM communicates the status of the A/C system pressure to the Body Control Module (SBM) via class 2 serial data. A higher pressure results in a higher voltage output. A/C pressure is constantly monitored to:
^ Disengage the A/C clutch if the pressures are high-2968 kPa (430 psi).
^ Disengage the A/C clutch if pressures are too low-below 255 kPa (37 psi).

A/C Compressor Control Relay
The A/C compressor control relay cycles the compressor on and off by energizing/de-energizing the compressor clutch coil.

With the ignition key on, 12 volts is applied to the relay common contact and one coil terminal. The second coil terminal is grounded by the PCM when the driver selects A/C or defrost modes and all other requirements are met.

When the relay is energized, current passes through the relay contacts which energizes the compressor clutch coil.