Cooling fans, like the thermostat, must be controlled so that the engine can maintain a constant temperature.
Cooling Fans for Front, Rear, and Four Wheel Drive
Cars that are front-wheel drive usually possess electrical fans because the engine is usually mounted transversely. This means that the engine's output is pointing to one of the sides of the car. These fans are typically controlled by either a thermostatic switch or by the engine's computer which activates when the temperature of the coolant rises above a pre-set point. After this, they will shut off when the temperature falls below that pre-set point.