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Home >> Oldsmobile >> 1999 >> Intrigue V6-3.8L VIN K >> Repair and Diagnosis >> Powertrain Management >> Computers and Control Systems >> Engine Control Module >> Description and Operation >> PCM Controlled Air Conditioning Description >> Operation

Operation

The air conditioning system uses a variable displacement compressor referred to as type V-5. The V-5 compressor meets A/C requirements without cycling. The A/C compressor operation is controlled by the Powertrain Control Module (PCM) for the following reasons:
^ Improved idle quality during compressor clutch engagement.
^ Improved wide open throttle performance (WOT).
^ Protects the A/C compressor from operation with incorrect refrigerant pressures.

The A/C clutch electrical system consists of the following components:
^ The A/C control head and/or the A/C programmer.
^ The A/C refrigerant pressure sensor.
^ The A/C compressor clutch.
^ The A/C compressor clutch relay.
^ The PCM.

When an A/C mode is selected, the A/C control head/programmer sends the A/C request signal to the PCM. The A/C compressor clutch relay is controlled by the PCM. The PCM provides a ground path for the A/C relay coil. The PCM will enable the A/C compressor clutch relay whenever the engine is running and the A/C has been requested by the A/C control head/programmer. When the A/C compressor relay is engaged, battery voltage is supplied to the compressor clutch coil. The PCM and the A/C control head/programmer monitor the A/C pressure sensor signal. If the A/C pressure sensor signal indicates an A/C pressure outside the normal operation range, the A/C control head/programmer will remove the A/C request signal from the PCM. The PCM will disengage the A/C relay.

The PCM will enable the A/C relay unless one or more of the following conditions are present:
^ Throttle angle is greater than 96%.
^ A/C head pressure is greater than 440 psi (4.6 volts) or less than 35 psi (0.4 volt) as determined by the A/C refrigerant pressure sensor.
^ Ignition voltage is less than 10.5 volts.
^ Engine speed is greater than 5400 RPM for any amount of time.
^ Engine speed is greater than 4300 RPM for longer than 1 seconds.
^ ECT is greater than 124°C (255°F).
^ IAT is less than 5°C (41°F).

Any of the conditions described above will inhibit A/C compressor relay operation.
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