A radiator temperature switch, also known as an engine coolant fan switch or thermoswitch, primarily works using a bimetallic disc that bends at a specific temperature, completing an electrical circuit and activating the radiator fan.
The Working Principle Explained
The radiator temperature switch is a critical component that ensures your engine doesn't overheat. Here's a breakdown of how it functions:
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Bimetallic Disc: The core of the switch is a bimetallic disc constructed from two different metals bonded together. These metals have different coefficients of thermal expansion, meaning they expand at different rates when heated.
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Temperature Sensitivity: The bimetallic disc is calibrated to "snap" or bend at a precise temperature. This temperature is chosen to correspond with the optimal point at which the radiator fan should activate to cool the engine coolant.
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Bending Action: As the engine coolant temperature rises and heats the switch, the two metals in the bimetallic disc expand at different rates. This differential expansion causes the disc to bend or deform.
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Contact Closure: When the bimetallic disc reaches its calibrated temperature and snaps, it physically moves a pin or lever. This movement closes an electrical circuit.
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Fan Activation: The closed circuit sends power to the radiator fan motor, causing the fan to start spinning. The fan draws air through the radiator, dissipating heat from the coolant and helping to lower the engine temperature.
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Deactivation: As the coolant temperature decreases, the bimetallic disc cools and returns to its original shape. This breaks the electrical circuit, stopping the fan.
In essence, the radiator temperature switch acts as a temperature-sensitive on/off switch that controls the radiator fan based on the engine coolant temperature.
Summary
The radiator temperature switch uses a bimetallic disc to sense coolant temperature. When the temperature reaches a preset threshold, the disc bends, closing an electrical circuit that activates the radiator fan to cool the engine. Once the temperature drops sufficiently, the disc returns to its original position, opening the circuit and switching off the fan.
