Masterparts stock a large supply of water temperature sensors.
A water temperature sensor or engine coolant temperature (ECT) sensor is screwed into the engine’s block, cylinder head or radiator and is used to determine the temperature of the engine coolant.
The sensor is basically a thermistor that changes resistance with temperature.
When the ECT is high (hotter), the resistance is low and when the ECT is low (cooler) the resistance is high.
This resistance reading is sent to the vehicle’s onboard computer and is used to regulate various ignition, fuel and emission control functions and to turn the radiator-cooling fan on and off as needed.