Strictly speaking, water and temperature sensors are divided into two categories. Either way, its internal structure is a thermistor, and its resistance is between 275 and 6500 ohms. And the lower the temperature, the higher the resistance, the higher the temperature, the lower the resistance. The role of the first type of water temperature sensor is relatively simple through the change of its internal resistance value to achieve through the change of the resistance of the sensor to change the current change to drive the change of the water temperature meter, indirectly tell people the working temperature of the engine. The second type of water temperature sensor has no change in structure, but its role is to provide an analog signal of temperature change to the engine control unit.