Compressor Controls

DESCRIPTION
In order to improve idle quality, wide open throttle performance, and to protect the system, the A/C compressor clutch is controlled by the Powertrain Control Module (PCM).

The system uses a compressor with a variable displacement, referred to as the V-5 type compressor. The V-5 type meets A/C requirements without cycling.

OPERATION
This system consists of an A/C select switch, a control relay and the compressor clutch. An A/C refrigerant pressure sensor is also used to indicate high side refrigerant pressure to the PCM for use in controlling the engine cooling fans, A/C compressor clutch and Idle Air Control (IAC) valve. A fault in the A/C refrigerant pressure sensor circuit should set a Diagnostic Trouble Code (DTC) P1530, which will cause the PCM to disable the compressor clutch.

The A/C refrigerant pressure sensor also provides low and high pressure protection for the system. If the A/C refrigerant pressure sensor signal exceeds about 4.7 volts. indicating pressure of about 436 psi, the compressor clutch is disabled. It will remain disabled until A/C refrigerant pressure sensor indicating about 211 psi. This protects the system from over-pressure.

If the A/C refrigerant pressure sensor voltage is less than about 0.6 volt, indicating about 38 psi the compressor clutch is disabled. It will remain disabled until the A/C refrigerant pressure sensor voltage signal rises above about 0.7 volt, indicating about 50 psi. This protects the system in case of loss of refrigerant and prevents the compressor from operating in cold weather.

The A/C compressor clutch control relay is controlled by the PCM so that the PCM can increase idle speed before turning
"ON" the clutch and can disable the clutch during WOT, high RPM, or during hot engine restarts. A/C is also disabled if coolant temperature exceeds 124°C.