A/C Mode

The purpose of the Air Conditioning (A/C) system is to provide cool air and remove humidity from the interior of the vehicle. The A/C system is engaged when the HVAC control module is in any mode. The A/C system can operate regardless of the temperature setting, as long as ambient temperature is above 3°C (38°F). The passenger and can adjust the temperature offset by adjusting the right air temperature switch. Passenger temperatures can be offset 2°C (4°F) cooler or warmer than the drivers setting

The HVAC control module is the interface between the vehicle operator and the HVAC control processor. When an A/C request is selected, a signal is sent tram the HVAC control processor to the Powertrain Control Module (PCM). The PCM monitors A/C refrigerant line pressure, A/C refrigerant temperatures and engine coolant temperature. If all the PCM signals are normal, the A/C clutch relay control circuit will be grounded, allowing the A/C compressor to engage. If there is a malfunction in the A/C system, the driver information center will read either SERVICE A/C SYSTEM or LOW REFRIG A/C OFF to alert the vehicle operator that there is a malfunction with the A/C system.

The PCM turns on the A/C compressor by providing a path to ground through the A/C clutch relay control circuit for the A/C compressor clutch relay. Power is provided to the A/C compressor clutch relay from the underhood fuse/relay block on the A/C low pressure switch signal circuit and both A/C pressure switches. Once the relay closes its internal switch, power from the battery is provided to the A/C compressor clutch through the A/C compressor clutch supply voltage circuit. The ground circuit provides a path to ground for the compressor. The A/C clutch relay control circuit is grounded internally within the PCM.

The PCM will open the A/C clutch relay control circuit when coolant temperatures get too hot or their is a loss of refrigerant. When engine coolant temperatures reach 126°C (259°F), the PCM will open the A/C clutch relay control circuit. When the PCM reads wide open throttle, the PCM will shut off the compressor for 20 seconds.