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 vehicle operator can activate the A/C system by activating the following modes:
^ MAX A/C
^ A/C
^ BI-LEVEL MIX-BLEND
^ FRONT DEFROST

The A/C system can operate regardless of the temperature setting, as long as the ambient air temperature is above 3°C (38°F). If the A/C compressor clutch is turned off due to cold ambient air temperatures, the compressor will not come back on until ambient air temperatures reach 5°C (41°F).

Regardless of the selected A/C mode setting, a request is made to the Powertrain Control Module (PCM) to turn on the A/C compressor clutch. The request is made through the A/C request signal circuit from the HVAC control assembly. Power and ground are provided to the HVAC control assembly by the ignition 3 voltage and ground circuits.

When the vehicle operator makes an A/C request, a 12 volt request signal is sent out over the A/C request signal circuit and grounded through the PCM. When this request signal is grounded, the PCM can activate the A/C compressor clutch.

The PCM turns on the A/C compressor clutch by providing a path to ground through the A/C compressor clutch relay control circuit for the A/C compressor clutch relay. Power is provided to the A/C compressor clutch relay from of the underhood fuse block on the ignition 1 voltage circuit. 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. Whenever the compressor is turned off, the A/C compressor clutch diode prevents a voltage spike from entering the vehicles electrical system. The ground circuit provides a path to ground for the compressor. The A/C compressor clutch relay control circuit is grounded internally within the PCM. On vehicles with the V8 option, an A/C compressor clutch status signal is sent to the PCM on the A/C compressor clutch supply voltage circuit.

The PCM will engage the A/C compressor clutch any time the engine speed is below 5000 RPM and the A/C is requested unless any of the wing conditions exist:
^ Throttle angle is at 100 percent (WOT).
^ Vehicle launch, hard acceleration from a stop.
^ Idle quality
^ The A/C refrigerant pressure sensor is above 2826 kPa (410 psi) or is less than 207 kPa (30 psi).
^ Engine speed is more than 5500 RPM.
^ Engine coolant temperature (ECT) is more than 121°C (250°F) for the L36 and 125°C (257°F) for the LS1.
^ Transmission shift
^ Engine torque load
^ Top of travel clutch switch position, if equipped