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Fan clutch

Simply Just, Simply SUNJIN

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What is a Fan Clutch?

A fan clutch is a device that automatically controls the rotational speed of the cooling fan based on engine temperature.
Used primarily in large commercial vehicles (trucks, buses, etc.), it prevents excessive power loss by operating the cooling fan only when necessary.

Key Components

Components explanation
Housing Clutch body, with silicone oil inside
Bimetal spring Controls operation by expanding/contracting according to temperature
Silicone oil Transmits or blocks the rotational power of the clutch
Drive plate Connected to a fan and rotated
Sensor/ECU (for electronic) Operation control based on temperature or vehicle condition

How it works

  • Mechanical Fan Clutch (Thermal Type)

When the coolant temperature is cold: The bimetallic spring is closed, causing the fan to spin slowly or stop. Increased fuel efficiency.

When the coolant temperature is hot: The spring opens and the silicone oil transmits the rotational force. The fan rotates quickly to cool down.

  • Electronically Controlled Fan Clutch
  • The ECU electronically controls clutch operation based on information such as temperature sensors, vehicle speed, and load.
  • Precise cooling control is possible, resulting in significant fuel savings.

Reasons and Benefits of Applying Electronic Fan Clutch in Commercial Vehicles

Merit Explanation
Improved fuel efficiency

Fan only runs when needed Reduce engine load

Noise reduction Prevent unnecessary fan rotation
Optimized cooling performance Temperature-adjusted operation prevents overheating
Extended engine life Maintains a constant temperature to protect the engine

Symptoms of failure

Symptoms Possible Causes
Poor cooling

Fan not spinning Clutch internal oil leak, bimetal failure

Fan continuous rotation Clutch internal sticking, electronic control signal error
Engine overheating Poor fan timing, temperature sensor, or ECU problem
Increased noise Bearing wear, clutch internal sticking