Cooling System: Description and Operation

Fans

How the Circuit Works
Battery voltage is supplied at all times through fuses 6 and 7 (in the under-hood fuse/relay box) to the contacts of the radiator fan relay and radiator fan relay respectively. With the ignition switch in ON (II), battery voltage is supplied through fuse 36 (in the under-dash fuse/relay box) to the A/C condenser fan relay coil. With the engine running, battery voltage is supplied through fuse 15 (in the under-hood fuse/relay box) to the radiator fan relay coil.

Extremely High Coolant Temperatures
In extremely high coolant temperature conditions (Above 206°F (97°C)), the PCM provides ground to the coils of the A/C condenser fan relay, the radiator fan relay, and the fan control relay energizing them. Battery voltage is supplied to the A/C condenser fan motor and radiator fan motor through their respective energized relays, which activates the motors at high speed.

A/C ON
The PCM detects that the A/C is ON through an input from the A/C pressure sensor. Upon receiving the A/C ON information, the PCM provides ground to the coil of the A/C condenser fan relay energizing it. Battery voltage is supplied to the radiator fan motor and A/C condenser fan motor in series through the energized relay, which activates the motors at low speed.

If the refrigerant pressure rises above 1520 kPa (221 psi)), the A/C pressure sensor signals the PCM to run the fans at high speed. The PCM provides ground to the coils of the A/C condenser fan relay, the radiator fan relay, and the fan control relay, energizing them. Battery voltage is supplied to the A/C condenser fan motor and radiator fan motor through their respective energized relays, which activates the motors at high speed.

Refrigerant at Low Pressure
If the refrigerant pressure drops below 196 kPa (28 psi), the A/C pressure sensor signals the PCM to turn off the fans. Upon receiving the signal to turn off the fans, the PCM removes ground from the coil of the A/C condenser fan relay, deenergizing it. This takes away battery voltage from the radiator fan motor and A/C condenser fan motor, which deactivates the motors.

Refrigerant at High Pressure
If the refrigerant pressure rises above 3140 kPa (455 psi), the A/C pressure sensor signals the PCM to turn off the fans. Upon receiving the signal to turn off the fans, the PCM removes ground from the coils of the A/C condenser fan relay, the radiator fan relay, and the fan control relay, deenergizing them. This takes away battery voltage from the A/C condenser fan motor and radiator fan motor, which deactivates the motors.