Cooling System: Description and Operation

Fans

How the Circuit Works

Fuses 6 and 7 (in the under-hood fuse/relay box) supply battery voltage at all times to the contacts of the A/C condenser fan relay and radiator fan relay respectively. With the ignition switch in ON (II), fuse 36 (in the under-dash fuse/relay box) supplies battery voltage to the radiator fan relay coil and the fan control relay coil. With the engine running, Fuse 11 (in the under-hood fuse/relay box) supplies battery voltage through the PGM-FI main sub-relay to the A/C condenser 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. The respective energized relays supply battery voltage to the A/C condenser fan motor and radiator fan motor. The energized fan control relay provides the ground for the radiator fan motor. Both motors run 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 radiator fan relay, energizing it. The energized relay supplies battery voltage to the radiator fan motor and A/C condenser fan motor in series, running 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. The respective energized relays supply battery voltage to the A/C condenser fan motor and radiator fan motor. The energized fan control relay provides the ground for the radiator fan motor. Both motors run 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, the PCM removes ground from the coil of the radiator fan relay, the fan control relay and the A/C condenser tan relay. This deactivates the fan 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, the PCM removes ground from the coil of the radiator fan relay, the fan control relay and the A/C condenser fan relay. This deactivates the fan motors.