Coolant Temperature Sensor/Switch (For Computer): Description and Operation

Coolant Temperature Sensor:

This sensor is located in the thermostat housing, and is in the flow of engine coolant so that it can monitor the coolant temperature. This sensor is a variable resistor whose resistance value is inversely proportional to the temperature of the engine (as the temperature of the engine increases, the resistance value decreases).

The Single Board Engine Controller (SBEC) monitors the voltage drop at the coolant temperature sensor. As the coolant temperature varies, so will the voltage drop at the sensor. The SBEC interprets these voltage drops to indicate one of many different scenarios possible, and once it receives these signals it will do one or more of the following:

^ Control engine warm-up idle speed.
^ Adjust the injector pulse width for the appropriate engine operating condition. The SBEC will increase the injector pulse width when the coolant temperature is cold resulting in a richer air-fuel mixture.
^ Turn the radiator fan ON or OFF.