For 1990-2009 cars

### General Description

The A/C compressor clutch is controlled by the powertrain control module (PCM). This allows the PCM to manage idle quality, improve wide open throttle (WOT) performance, and to protect the A/C system from excessively high and low pressures.

The PCM controlled air conditioning system uses a variable displacement compressor referred to as a V-5 compressor. The V-5 compressor meets the A/C requirements without cycling.

### Operation

The PCM controlled air conditioning system consists of an A/C compressor clutch relay, an A/C compressor clutch and an A/C refrigerant pressure sensor. The instrument panel cluster (IPC) and the A/C select switch also input the PCM through the UART serial data circuit.

The A/C refrigerant pressure sensor is used to indicate high side pressures. The PCM uses this information to control the cooling fan operation, the A/C compressor clutch operation and the idle speed. A fault in the A/C refrigerant pressure sensor circuit will set a DTC P0530. This will cause the PCM to disable the A/C compressor clutch compressor.

The PCM determines high and low pressures in the A/C system by the voltage signal it receives from the A/C refrigerant pressure sensor. This allows the PCM to protect the A/C system from excessively high and low pressures. If the A/C refrigerant pressure sensor voltage exceeds about 4.7 volt, indicating pressure of 428 psi, the PCM will disable the A/C compressor clutch. The A/C compressor clutch will remain disabled until the A/C refrigerant pressure sensor voltage falls below 1.98 volt, indicating about 170 psi.

The PCM will temporarily disable the A/C compressor clutch during the following conditions:

• | A wide open throttle

• | A high RPM

• | High power steering loads

• | Hot engine re-starts

• | If the engine coolant temperature exceeds 125°C (257°F)