Operation
The air-conditioning system uses a compressor with variable displacement.
This compressor is referred to as the V-5 type compressor. The V-5 compressor
meets the A/C requirements without cycling. The Powertrain Control Module
(PCM) controls the A/C compressor operation 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 |
When an A/C mode is selected at the A/C control head, the A/C programmer
provides a 12-volt signal to the A/C request circuit. The PCM monitors the
A/C request circuit and controls the A/C compressor relay based on the A/C
request signal. This allows the PCM to increase the engine idle speed just
prior to A/C clutch engagement for better idle quality. In addition, the
PCM will command the cooling fans ON during A/C operation. The PCM also
monitors the A/C refrigerant pressure sensor circuit. If the A/C refrigerant
pressure is too high or too low, the PCM will disable the A/C compressor
relay.
The PCM will enable the A/C compressor clutch whenever the engine is
running and the A/C has been requested unless one or more of the following
conditions are present:
| • | The throttle angle is more than 96%. |
| • | The A/C head pressure is more than 440 psi (4.6 volts)
or less than 33 psi (0.3 volt), as determined by the A/C refrigerant
pressure sensor. |
| • | The ignition voltage is less than 10 volts. |
| • | The engine speed is more than 4400 RPM for any of time. |
| • | The engine speed is more than 4392 RPM for less than 1 second. |
| • | The ECT is more than 124°C (255°F). |
| • | The IAT is less than 5°C (41°F). |
Any of the conditions described above will inhibit the A/C
compressor relay operation.
