Fan Clutch refers to an automatic device frequently used in automotive cooling systems. When the engine is cool or even at normal operating temperature, the fan clutch partially disengages the engine's mechanically-driven radiator cooling fan, generally located at the front of the water pump and driven by a belt and pulley connected to the engine's crankshaft. This saves power since the engine does not have to fully drive the fan. Car redirects here. ... A pump is a mechanical device used to move liquids or gases. ... A pulley is a wheel with a groove along its edge, for holding a rope or cable. ... Crankshaft Continental engine marine crankshafts, 1942 Crankshaft is also the name of a comic strip about an old, curmudgeonly bus driver. ...

However, if engine temperature climbs beyond the clutch's pre-determined setting, the fan becomes fully engaged, thus maintaining or lowering engine temperature.

Most fan clutches are viscous or "fluid" couplings combined with a bi-metallic sensory system similar to that in a thermostat. Viscosity is a measure of the resistance of a fluid to deformation under shear stress. ... thermocouple and Peltier_Seebeck effect. ... Bi-metallic thermostat for buildings A thermostat is a device for maintaining the temperature of a system within a range by controlling, either directly or indirectly, the flow of heat energy into or out of the system. ...

Normally fan clutches are fairly reliable, but sometimes they fail. A common symptom of fan clutch failure is overheating at idle. Bad fan clutches can also cause poor performance of the car's air conditioning system because the fan also cools the air conditioner's condenser, which is directly in front of the radiator.

Another potential symptom if the fan clutch fails (always drawing air at a high rate)in a cold weather climate is that the heating system blows lukewarm air never delivering enough sufficient hot air.