The cooling fan is designed to draw air through the radiator and air conditioning condenser to remove heat from the A/C refrigerant and the engine’s coolant. A direct drive, or belt driven fan, is mounted on a temperature-controlled clutch that draws air once the physical temperature at the fan is hot. An electric fan operates differently. When the engine temperature increases, the fans come on in stages, which are controlled by a resistor. When the engine is turned on, the temperature rapidly increases. The resistor is powered by the ignition and enables the cooling fan to run at slow speed. Once the engine reaches a manufacturer-predetermined temperature, a temperature switch indicates to the cooling fan resistor that the fan should run at high speed to draw more air through the radiator and provide extra cooling. If there is a second fan, its purpose is to provide even more airflow for the air conditioning and cooling system. When the air conditioning is turned on, the resistor supplies power to the second fan, which always runs at high speed.
Many cooling system fans will continue to run after the engine is turned off to rapidly drop the engine temperature. If the radiator fan resistor is shorted, one of the cooling fan modes may not work, the cooling fan may not turn off when the engine is cold, or the cooling fans may not come on at all.
The cooling fan resistor doesn’t require regular maintenance. If you suspect issues with your cooling fan, have one of our expert technicians diagnose and repair it. If the cooling fan is being replaced, it would be prudent to replace the resistor at the same time.
The engine will not run optimally if the temperature is too hot or too cold. You run the risk of overheating the engine if the cooling fan will not run at all, which could result in additional, costly repairs. Have the cooling fan resistor replaced as soon as it fails.
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