Condenser Fan Circuit Operation

When the ignition switch is in the ON position, system voltage is applied to the coil side of the condenser fan relay through the DEF fuse.

System voltage is applied to the switch side of the condenser fan relay through the HTR fuse at all times.

The Powertrain Control Module (PCM) grounds the A/C condenser fan relay coil under any of the following conditions:
^ The A/C system is operating.
^ The Engine Coolant Temperature (ECT) is 110°C (230°F) or higher.
^ The PCM detects an Engine Coolant Temperature (ECT) sensor malfunction.

When the relay is energized, battery voltage is applied to the A/C condenser fan through the A/C fuse and the contacts of the relay. Since the A/C condenser fan is permanently grounded at G105, the [1][2]condenser fan operates as long as the relay is energized.

The A/C compressor control module monitors the evaporator temperature sensor that is mounted inside the evaporator housing. The evaporator temperature sensor converts the evaporator core temperature into a resistance value. Using this resistance value, the A/C compressor control module can sense when the evaporator temperature drops below 0°C (32°F). When this occurs, the A/C compressor control module removes the A/C clutch relay coil ground and the PCM removes the A/C condenser fan relay coil ground. This prevents evaporator frost and ice-up which reduces air flow and reduces the unit's cooling capacity.

Whenever the pressure in the A/C system drops below 193 kPa (28 psi) or rises above 3137 kPa (455 psi), the refrigerant pressure sensor opens. This signals the A/C compressor control module to interrupt voltage to the A/C compressor clutch and signals the PCM to interrupt voltage to the condenser fan motor.