Radiator Fan
An electric or engine-driven fan that pulls cool air through the radiator core to dissipate engine heat when speed is low.
The radiator fan is an essential cooling system component located behind or in front of the radiator. Its job is to pull air through the radiator core to cool the hot engine coolant flowing inside, particularly when the vehicle is stationary or moving slowly.
At highway speeds, natural airflow passing through the grille is sufficient to cool the radiator. However, when idling in traffic or driving at low speeds, natural airflow drops. The radiator fan turns on to generate the airflow needed to prevent the engine from overheating.
Modern vehicles typically use electric radiator fans controlled by the Engine Control Unit (ECU) via a relay. The ECU monitors coolant temperature and switches the fan on when a set limit is reached. Older trucks and SUVs use mechanical fans driven by the engine's serpentine belt via a thermostatic fan clutch.
A failed radiator fan will cause the engine temperature to spike rapidly when idling, which can lead to severe engine damage. Common causes of fan failure include burnt electric motors, failed relays, blown fuses, or a faulty coolant temperature sensor.