In order to improve engine operation, and protect the A/C
compressor and A/C clutch during Wide Open Throttle (WOT) performance, the
A/C compressor operation is controlled by the PCM.
This A/C system consists of the following components:
| • | The heater and A/C control |
| • | The A/C pressure cycling switch |
| • | The A/C refrigerant pressure sensor |
| • | The A/C compressor clutch |
The A/C refrigerant pressure cycling switch is closed when there is
sufficient system pressure (depending on refrigerant charge and ambient temperature).
When the heater and A/C control is placed in the A/C mode, a request signal
is sent to the PCM. The PCM will then energize the A/C clutch relay, unless
abnormally high or low A/C pressure is detected by the A/C refrigerant pressure
sensor. The PCM will also turn the cooling fans ON when A/C is requested.
The A/C clutch relay is controlled by the PCM so that the PCM can increase
idle speed before turning ON the clutch or disable the clutch during WOT,
or high coolant temperature.
The PCM will energize the A/C clutch whenever the engine
is running less than 4100 RPM and A/C has been requested, unless any
of the following conditions are met:
| • | Wide Open Throttle (WOT). |
| • | A/C head pressure greater than 431 psi or less than 0 psi
(as determined by the A/C refrigerant pressure sensor). |
| • | Ignition voltage less than 10 volts. |
| • | Engine speed greater than 5550 RPM for 180 seconds. |
| • | ECT greater than 124°C (256°F). |
The A/C Request Table should be used for diagnosing the A/C request
circuit only. Refer to Section 1B or 1C of the appropriate service manual
should be used for diagnosing the refrigerant portion of the system.
The scan tool will be used in diagnosing the system. The PCM has the
ability to display the following parameters:
| • | A/C request input to the PCM |
| • | A/C clutch ON or OFF status |
Refer to Heater Ventilation and Air Conditioning (HVAC)
for service procedures.
