System Operation

The PCM controlled air conditioning system consists of an A/C compressor clutch relay, an A/C compressor clutch and an A/C refrigerant pressure sensor. The PCM receives an A/C request signal from the A/C selector switch. When A/C is requested, the Powertrain Control Module (PCM) provides a ground path to the A/C clutch relay control circuit. When the relay circuit is grounded, the A/C compressor clutch relay is energized. The PCM delays grounding the relay circuit for 0.3 second, so the PCM can adjust the engine idle RPM for the additional load. The PCM will temporarily de-energize the A/C compressor clutch relay for one or more of the following conditions:
^ A hot engine restart.
^ A wide open throttle (TP sensor over 90 percent).
^ Engine RPM more than 6000 RPM.
^ During an Idle Air Control (IAC) valve reset. The A/C compressor clutch relay will remain de-energized when one or both of the following conditions exist:
^ A DTC P0530 is set.
^ There is no A/C request signal to the PCM. Refer to Refrigerant System Checks in Heating and Air Conditioning for more information on the A/C refrigerant systems.