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 refrigerant pressure sensor |
| • | The A/C compressor clutch |
When the heater and A/C control is placed in the A/C mode, a request
signal is sent to the PCM. The PCM then energizes the A/C clutch relay,
unless abnormally high or low A/C pressure is detected by the
A/C refrigerant pressure sensor. The PCM also turns 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 A/C compressor clutch or disable the A/C compressor clutch
during WOT, or high coolant temperature.
The PCM energizes the A/C clutch whenever the engine is
running less than 3950 RPM and A/C has been requested. The PCM will
not energize the A/C clutch whenever any of the following conditions
are present:
| • | Throttle Angle greater than 86 percent. |
| • | A/C head pressure greater than 414 psi or less than 0 psi
(as determined by the A/C refrigerant pressure sensor). The PCM re-enables
the A/C system when the A/C high side pressure is less than 249 psi. |
| • | Ignition voltage less than 10 volts. |
| • | Engine speed greater than 4294 RPM. |
| • | ECT greater than 125°C (257°F). The PCM re-enables the
A/C at 121°C (250°F). |
The scan tool is used in diagnosing the A/C system. The PCM has the
ability to display the following parameters:
| • | A/C request input to the PCM |
| • | A/C system refrigerant pressure |
| • | A/C clutch ON or OFF status |
