Cooling System: Description and Operation

On models less A/C, the cooling fan is actuated by a thermo sensor located in the radiator tank. Battery voltage is applied to the cooling fan when the ignition switch is in the On position, and the cooling fan ground circuit is completed through the thermo sensor. When coolant temperature is below 190°F, the thermo sensor contact is open and the cooling fan does not run. When coolant temperature exceeds 190°F, the contact in the thermo sensor closes and the cooling fan runs whenever the ignition switch is in the On position.

On models with A/C, a relay is added to the cooling fan control circuit. Battery voltage is applied to the relay through the ignition switch, and voltage is applied to the cooling fan through the relay switching circuit. The relay control coil ground path is completed either through the thermo sensor or through the A/C compressor clutch switch. When the engine is running and the relay control coil ground circuit is completed, voltage is applied to the cooling fan motor and the fan operates.

During normal operation, the thermo sensor contacts close when coolant temperature is approximately 190°F, and voltage is applied to the cooling fan motor. When coolant temperature is below 190°F, the thermo sensor contacts are open and the cooling fan does not operate. However, when the A/C clutch is energized, the fan relay coil circuit is completed to ground through the A/C switch and the cooling fan operates regardless of coolant temperature.