If it is on the car, it is generally NTC type, that is, negative temperature coefficient sensor, the general room temperature resistance is more than 2K ohms, and the 90 degree water temperature is about 200 ohms, because the sensor manufacturers and models are slightly different. Measurement method: Use a multimeter resistance profile measurement, some are two lines, direct positive and negative pen with two pins on the line, three lines are generally triangle pins or a font pin, triangle pins of the bottom side of the two feet, a font pin of the measuring side of the two feet, triangle top Angle and a font of the middle pin is generally received by the car instrument. Depending on the model, it is roughly 90 degrees, but the fan is generally divided into high and low gear, the low gear starts at about 87 degrees, if the fan is turning at this time, and the water temperature continues to rise, after reaching 95 degrees, the high-speed fan begins to work, the low speed has 87 degrees of 85 degrees, the high speed has 95 degrees of 97 degrees, depending on the model. You can refer to the specific model. The detection method of water temperature sensor: using a digital resistance simulator to simulate the water temperature and temperature, comparing with the actual situation, testing the actual temperature of the water temperature sensor with an infrared thermometer, testing the resistance value of the water temperature sensor with a multimeter compared with the water temperature meter, heating the water temperature sensor with a hair dryer, and reducing the resistance value of the water temperature sensor with a multimeter to test the resistance value of the water temperature sensor and testing the water temperature temperature with an infrared thermometer. And with the maintenance manual temperature and resistance values.