Circuit Description
When an A/C mode is selected, the A/C control head or the A/C programmer supplies a 12 volt signal to the PCM A/C request input. The A/C compressor clutch relay is controlled by the PCM. The PCM provides a ground path for the A/C relay coil. When the A/C compressor relay is engaged battery voltage is supplied to the compressor clutch coil. 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 90 percent. |
| • | The A/C head pressure is more than 414 psi (4.27 volts) or less than 34 psi (0.35 volt) as determined by the A/C refrigerant pressure sensor. |
| • | The ignition 1 voltage is less than 10 volts. |
| • | The engine speed is more than 4225 RPM for more than 5 second. |
| • | The engine speed is more than 5280 RPM for any amount of time. |
| • | The engine coolant temperature (ECT) is more than 125°C (257°F). |
| • | The intake air temperature (IAT) is less than 0°C (32°F). |
Any of the conditions described above will inhibit A/C compressor relay operation.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||
2 | Are any PCM DTCs stored? | -- | Go to Diagnostic System Check or to Diagnostic System Check |
