Fan Clutch : This allows a cooling fan attached to an engine to spin or be released from spinning with the engine speed. Most fan clutches are made of a metal housing with a hydraulic oil inside. The turbine blades inside help regulate the fan speed with the centrifugal force or the spinning engine speed. Some fan clutches also use a temperature absorbent spring to help stiffen or loosen the can clutch speed with the temperature of the engine. Other fan clutches are computer controlled with an electrical clutch applied only when commanded by a computer. The computer uses an ac switch signal as well as a engine coolant temperature sensor to determine when to turn on or off the fan clutch.
Fan clutches can leak hydraulic fluid and go bad. If they develop a leak, the fan clutch must be replaced. Other fan clutch problems may be internal failure causing a weak fan speed or bearing noise within the fan clutch. Electric fan clutches can get a bad electro magnet problem which keeps the fan clutch from engaging.