Temperature sensors are resistors that varies the voltage output as the temperature changes. Its mechanism is simple. When the temperature of your machine or whatever you’re measuring decreases, its resistance increases.
To illustrate, when your temperature, say in your engine is at 32 degrees Fahrenheit, you can expect your resistance to be between 4800-6600 ohms.
If your engine temperature is at 176 degrees Fahrenheit, your resistance would be at 270-380 ohms.
See the inverse relationship between the two?
Higher temperatures will generally decrease the resistance between the two terminals.
When performing resistance test on the sensor, it is important to disconnect the electrical connector. You can test your coolant temperature sensor by using the ohm setting on your voltmeter. This way you can test the resistance between the two terminals.
The sensor is usually located is near the thermostat housing.