Car Fans are controlled by either a thermostatic switch or by the engine's computer, like thermostats, a
work to ensure that the engine maintains a constant temperature.
When the temperature of the coolant rises above a set level, perhaps the car is stationary and there is no cool air moving through the grill to dissipate heat from the radiator, the fan kicks in, blowing cooler air through the radiator to help the cooling process. Car cooling fans for any car are quickly and easily available at Eurocarparts.com. Most modern radiator cooling fans are specially designed to work on the basis of a thermostatic switch.