Engine temperature switch 2W8915 7N9785 2W-8915 7N-9785 3406B 3406C 3408 3408B 3408C 3412 3412C

Engine Temperature Switch 2W8915 7N9785 2W-8915 7N-9785 3406B 3406C 3408 3408B 3408C 3412 3412C

The bulldozer engine temperature switch (commonly known as a temperature control switch or coolant temperature switch) is a key component of the engine cooling system, primarily used to monitor and control the engine's operating temperature. Its core function is to sense the coolant temperature and trigger a circuit when the temperature reaches a preset value to adjust the cooling fan's operation, ensuring the engine operates within a suitable temperature range.

Main Functions

Cooling Fan Control: When the coolant temperature exceeds a set threshold (e.g., 95℃ or 105℃), the temperature control switch connects the circuit, activating the cooling fan for forced cooling; when the coolant temperature drops, the circuit disconnects, stopping the fan.

Engine Protection: Prevents engine overheating, power loss, or even stalling due to excessively high temperatures, avoiding serious mechanical damage.

In conjunction with other sensors: In some models, the temperature control switch works in conjunction with the coolant temperature sensor, responsible for fan control and ECU signal feedback, respectively.

Working Principle

Bimetallic Strip Type: Utilizes the difference in thermal expansion coefficients between two metals; deformation due to temperature changes triggers the contact to open or close.

Paramesu-Driven Type: Thermoplastic expands when heated, pushing a push rod to control multiple contact points (e.g., low/high speed fan).

Thermocouple Type: Sends a temperature signal to the ECU via resistance changes, allowing the computer to control the fan.