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.
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.
