Operation

When an A/C mode is selected at the A/C control head, the A/C control head provides a 12 volts 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 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 any of the following conditions are met:
^ Throttle greater than 90%.
^ A/C head pressure greater than 414 psi (4.27 volts) or less than 34 psi (0.35 volt) (as determined by the A/C refrigerant pressure sensor).
^ Ignition voltage below 10.5 volts.
^ Engine speed greater than 4500 RPM for 5 seconds or 5400 RPM.
^ ECT greater than 125°C (257°F).
^ IAT less than 5°C (41°F).