Compressor Controls

DESCRIPTION
The A/C compressor clutch is controlled by the Powertrain Control Module (PCM). This allows the PCM to manage idle quality, to improve wide open throttle 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 select switch, an A/C compressor clutch relay, an A/C compressor clutch and an A/C refrigerant pressure sensor.

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 should 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 4.7V, indicating pressure of about 2951 kPa (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 about 1.98V, indicating about 1172 kPa (170 psi).

If the A/C refrigerant pressure sensor voltage is less than about 0.62V, indicating about 296 kPa (43 psi) the PCM will disable the A/C compressor clutch. It will remain disabled until the A/C refrigerant pressure sensor voltage signal rises above about 0.72V, indicating about 359 kPa (52 psi). This protects the system, from the loss of refrigerant and prevents the A/C compressor clutch from operating in cold weather.

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

- Wide Open Throttle (WOT).
- High RPM(s).
- High power steering loads.
- Hot engine re-starts.
- Engine coolant temperature exceeding 125°C.

Refer to Chart C-10 A/C Clutch Control Circuit for specific wiring, circuit and calibration description. Testing and Inspection