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

Engine Coolant Sensor:

PURPOSE
Information concerning the engine operating temperature is supplied by the coolant temperature sensor. The resistance value produced by the sensor is used by the DME control unit to correct fuel injector opening time for cold starting and warm-up periods.

OPERATION
The sensor is a NTC type (negative temperature co-efficient) in which the resistance value of the sensor decreases as the temperature of the coolant increases. If the sensor becomes defective (open circuit) the engine may run very rich until the DME control unit has time to implement a substitute value and an emergency run program.