Your vehicle’s electric fan switch turns on the cooling fan when your engine gets too hot. When the temperature reaches the switch’s pre-set threshold, an internal circuit turns on the fan. When the temperature drops back down, the fan turns off. If the switch is faulty, the fan may not turn on when it should or may run constantly, even when the engine is off. A properly working thermostatic fan switch is crucial to prevent engine overheating that can cause damage to or complete failure of your engine. If your temperature gauge climbs higher than normal and the fan doesn’t come on or if your Check Engine light comes on, this could indicate a faulty electric fan switch that needs to be replaced immediately.