Cooling System: Description and Operation

Cooling fan operation is controlled by the fan timer module which monitors signals from coolant temperature sensor, and A/C compressor clutch operation. Timer operates cooling fan by controlling voltage applied to fan relay control coil. Battery voltage is applied directly from main fuse to relay switch circuit and timer bypass circuit. Voltage is applied to timer main circuits through ignition switch start and run contacts. Timer module controls voltage applied to relay control coil circuit, and control coil circuit is completed to ground through either thermo sensor or timing module. When current flows through relay coil circuit, relay contacts close and voltage is applied to cooling fan motor.

During normal operation, voltage is applied to relay coil by timer module and fan operation is thermo sensor controlled. When coolant temperature is approximately 190°F, current flows through relay coil circuit and voltage is applied to fan motor. When coolant temperature is below 190°F, thermo sensor contacts open and cooling fan does not operate. When A/C is turned on, timer energizes relay coil and cooling fan operates as long as clutch remains energized.

When engine is turned off, timer module remains energized and monitors signals from coolant temperature sensor. If underhood temperature exceeds 220°F, timer activates fan relay and cooling fan is energized. Cooling fan will operate for a maximum of 15 minutes after engine has stopped or until underhood temperature drops below 220°F.