Fan clutch
Encyclopedia
A fan clutch is a thermostatic device that exists as an integral component of certain 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 rises above the clutch's engagement temperature setting, the fan becomes fully engaged, thus drawing a higher volume of ambient air through the vehicle's radiator, which in turn serves to maintain or lower the engine coolant
temperature to an acceptable level.
Mechanical fans are most common in trucks and SUVs, and some RWD cars. This is easier to accomplish because the engine is mounted longitudinally, with the belt accessory components mounted facing the radiator. The fan will spin in between the radiator and the engine to help with cooling.
Most fan clutches are viscous or "fluid" couplings, combined with a bi-metallic sensory system similar to that in a thermostat
. Some clutches are electronically controlled (in place of the bi-metallic strip). These provide the potential to control the level of engagement depending on any number of inputs. Common controlling factors might include engine oil temperature, transmission oil temperature, coolant temperature, AC system pressures and ambient air temperature.
A fan clutch is as reliable as any other component on a vehicle, yet sometimes they fail. A common symptom of fan clutch failure is overheating at idle or in heavy traffic. 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. A fan clutch can also fail in a stuck on position where engine power is lost even when the fan is not necessary. This type of failure can also decrease fuel economy.
Another potential symptom of fan clutch failure (always drawing air at a high rate) in a cold weather climate is that the heating system blows lukewarm air never delivering sufficient hot air.
The bearings in the fan clutch can be worn, causing extra grinding sound from the engine area.
Operating temperature
An operating temperature is the temperature at which an electrical or mechanical device operates. The device will operate effectively within a specified temperature range which varies based on the device function and application context, and ranges from the minimum operating temperature to the...
, the fan clutch partially disengages the engine's mechanically-driven radiator
Radiator (engine cooling)
Radiators are used for cooling internal combustion engines, mainly in automobiles but also in piston-engined aircraft, railway locomotives, motorcycles, stationary generating plant or any similar use of such an engine....
cooling fan
Fan (mechanical)
A mechanical fan is a machine used to create flow within a fluid, typically a gas such as air.A fan consists of a rotating arrangement of vanes or blades which act on the air. Usually, it is contained within some form of housing or case. This may direct the airflow or increase safety by preventing...
, generally located at the front of the water pump
Water Pump
Water Pump is one of the neighbourhoods of Gulberg Town in Karachi, Sindh, Pakistan. It is near main Water Pump that supplies fresh water to the city of Karachi....
and driven by a belt and pulley
Pulley
A pulley, also called a sheave or a drum, is a mechanism composed of a wheel on an axle or shaft that may have a groove between two flanges around its circumference. A rope, cable, belt, or chain usually runs over the wheel and inside the groove, if present...
connected to the engine's crankshaft
Crankshaft
The crankshaft, sometimes casually abbreviated to crank, is the part of an engine which translates reciprocating linear piston motion into rotation...
. This saves power, since the engine does not have to fully drive the fan.
However, if engine temperature rises above the clutch's engagement temperature setting, the fan becomes fully engaged, thus drawing a higher volume of ambient air through the vehicle's radiator, which in turn serves to maintain or lower the engine coolant
Coolant
A coolant is a fluid which flows through a device to prevent its overheating, transferring the heat produced by the device to other devices that use or dissipate it. An ideal coolant has high thermal capacity, low viscosity, is low-cost, non-toxic, and chemically inert, neither causing nor...
temperature to an acceptable level.
Mechanical fans are most common in trucks and SUVs, and some RWD cars. This is easier to accomplish because the engine is mounted longitudinally, with the belt accessory components mounted facing the radiator. The fan will spin in between the radiator and the engine to help with cooling.
Most fan clutches are viscous or "fluid" couplings, combined with a bi-metallic sensory system similar to that in a thermostat
Thermostat
A thermostat is the component of a control system which regulates the temperature of a system so that the system's temperature is maintained near a desired setpoint temperature. The thermostat does this by switching heating or cooling devices on or off, or regulating the flow of a heat transfer...
. Some clutches are electronically controlled (in place of the bi-metallic strip). These provide the potential to control the level of engagement depending on any number of inputs. Common controlling factors might include engine oil temperature, transmission oil temperature, coolant temperature, AC system pressures and ambient air temperature.
A fan clutch is as reliable as any other component on a vehicle, yet sometimes they fail. A common symptom of fan clutch failure is overheating at idle or in heavy traffic. Bad fan clutches can also cause poor performance of the car's air conditioning
Air conditioning
An air conditioner is a home appliance, system, or mechanism designed to dehumidify and extract heat from an area. The cooling is done using a simple refrigeration cycle...
system because the fan also cools the air conditioner's condenser
Condenser (heat transfer)
In systems involving heat transfer, a condenser is a device or unit used to condense a substance from its gaseous to its liquid state, typically by cooling it. In so doing, the latent heat is given up by the substance, and will transfer to the condenser coolant...
, which is directly in front of the radiator. A fan clutch can also fail in a stuck on position where engine power is lost even when the fan is not necessary. This type of failure can also decrease fuel economy.
Another potential symptom of fan clutch failure (always drawing air at a high rate) in a cold weather climate is that the heating system blows lukewarm air never delivering sufficient hot air.
The bearings in the fan clutch can be worn, causing extra grinding sound from the engine area.