Cooling System: Description and Operation

Fans

How the circuit works

Power Supply
When the PGM-FI main relay 1 is closed, battery voltage is supplied to the coil of the radiator fan control unit relay through fuse 23 (in the driver's under-dash fuse/relay box). Battery voltage is also supplied at all times (directly from the battery) to the switch contacts of the radiator fan control unit relay.

When the switch contacts of the radiator fan control unit relay are closed, the A/C condenser fan motor and the radiator fan motor are supplied with battery voltage.

High Coolant Temperatures
In high coolant temperature conditions (above 207 degrees F (97 degrees C)) the radiator fan control unit provides a ground to the A/C condenser fan motor and to the radiator fan motor, which activates the motors at high speed.

A/C ON
The climate control unit transmits "A/C ON" information through the B-CAN and F-CAN network of the multiplex system. Upon receiving the "A/C ON" information, the radiator fan control module unit provides a ground to the A/C condenser fan and to the radiator fan motor to run the motors. The fans run whenever the A/C compressor is activated.

If the refrigerant line pressure rises above 1,470 kPa (213 psi)), the A/C pressure sensor signals the climate control unit to run the run the fan motors at high speed.

The A/C request information is communicated through the B-CAN and F-CAN networks of the multiplex system.

Refrigerant at Low Pressure
If the refrigerant line pressure drops below 193 kPa (28 psi), the A/C pressure sensor signals the climate control unit to turn the A/C compressor off. The radiator fan control unit will then remove the grounds from the fan motors and turn the fans off.

The A/C request information is communicated through the B-CAN and F-CAN networks of the multiplex system.

Refrigerant at High Pressure
If the refrigerant line pressure raises above 3140 kPa (455 psi), the A/C pressure sensor signals the climate control unit to deactivate the A/C compressor. The radiator fan control unit will then remove the grounds from the fan motors and turn the fans off.

The A/C request information is communicated through the B-CAN and F-CAN networks of the multiplex system.