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

Fig. 28 Coolant Temperature Sensor:

The coolant temperature sensor, Fig. 28, is a negative temperature coefficient resistor (resistance increases as the temperature decreases). It is located in the cylinder head next to the #1 spark plug. The resistance signal is used by the control unit to advance the ignition timing when the engine is cold and the manifold pressure is below 1.0 bar (0 in. vacuum). The temp sensor signal is also used to correct the fuel mixture for various temperature conditions.