Cooling System: Description and Operation

Fans

How the Circuit Works
Battery voltage is supplied at all times through fuses 9 and 11 to the contacts of the A/C condenser fan relay and radiator fan relay respectively. With the ignition switch in ON (II), Battery voltage is supplied through fuse 30 to the A/C condenser fan relay coil. With the engine running, battery voltage is supplied through fuse 23 to the radiator fan relay coil.

Extremely High Coolant Temperatures
In extremely high coolant temperature conditions (Above 206 degrees F (97 degrees C)), the ECM/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 relay control module detects that the A/C is ON when the climate control unit grounds the 12 V reference voltage sent through the A/C pressure switch. The relay control module communicates this information to the ECM/PCM through the B-CAN and F-CAN networks of the multiplex system. Upon receiving the A/C ON information, the ECM/PCM provides ground to the coil of the A/C condenser fan relay energizing it. Battery voltage is supplied to the A/C condenser fan motor and radiator fan motor in series through the energized relay, which activates the motors at low speed.

If the refrigerant pressure rises above 1470 kPa (213 psi)), the A/C pressure switch closes which signals the ECM/PCM to run the fans at high speed. The ECM/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 lowers below 196 kPa (28 psi), the A/C pressure switch opens removing ground from the 12 V reference voltage. The relay control module detects that the A/C pressure switch is open, and the A/C needs to be turned OFF The relay control module communicates this information to the ECM/PCM through the B-CAN and F-CAN networks of the multiplex system. Upon receiving the A/C OFF information, the ECM/PCM removes ground from the coil of the A/C condenser fan relay deenergizing it. This takes away battery voltage from the A/C condenser fan motor and radiator fan motor, which deactivates the motors.

Refrigerant at High Pressure
If the refrigerant pressure rises above 3140 kPa (455 psi), the A/C pressure switch opens removing ground from the 12 V reference voltage. The relay control module detects that the A/C pressure switch is open, and the A/C needs to be turned OFF The relay control module communicates this information to the ECM/PCM through the B-CAN and F-CAN networks of the multiplex system. Upon receiving the A/C OFF information, the ECM/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.