General Information

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 depressing the A/C switch or by placing the mode control in Defrost position. The blower switch must be in any position except OFF for the A/C system to operate. The A/C system can operate regardless of the temperature setting.

Regardless of the selected A/C mode setting, a request is made to the A/C compressor control module to turn on the A/C compressor. The request is sent to the A/C compressor control module through the A/C request signal circuit from the defrost switch or from the A/C switch.

The A/C compressor control module and the A/C switch each receive ignition voltage through the IG fuse in the junction block. The defrost switch is in parallel with the A/C switch. The A/C compressor control module is grounded at G103. The A/C request circuit is grounded through the blower switch at G201 when the blower switch is in any position except OFF and either the A/C switch or the defrost switch is closed.

When the A/C switch is depressed, and the blower switch is in any position except OFF, a Light Emitting Diode (LED) within the A/C switch illuminates by grounding through the blower switch at G201. When the A/C compressor control module receives an A/C request, the A/C compressor control module provides a signal to the Powertrain Control Module (PCM) for idle control.

In order for the A/C compressor control module to internally ground the A/C clutch relay control circuit, the A/C refrigerant pressure switch must be closed and the evaporator temperature sensor must correspond to an evaporator core temperature of 0°-25°C (32°-77°F). With both these reference signals, the A/C compressor control module can activate the A/C compressor clutch.

The A/C compressor control module 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. Ignition voltage is provided to the A/C compressor clutch relay coil from the DEF fuse in the junction block. Battery voltage is provided to the A/C compressor clutch relay switch through the HTR fuse in the fuse block. 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 on, the A/C compressor clutch diode prevents a voltage spike from burning up the compressor clutch coil. The engine block provides a pathway to ground for the compressor. The A/C clutch relay control circuit is grounded internally within the A/C compressor control module.