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

Coolant Temperature Sensor:

PURPOSE
The coolant temperature sensor sends signals to the control module so that it can control injection time and idle speed in relation to engine temperature.

DESIGN
The coolant temperature sensor is of the Negative Temperature Co-efficient (NTC) type. This means the higher the coolant temperature, the lower the sensor resistance.

OPERATION
The ECU applies a regulated constant voltage to the sensor, and monitors the voltage in the circuit. As temperature increases, sensor resistance decreases, causing a decrease in the measured voltage of the circuit.

By monitoring the circuit voltage, the ECU can calculate the engine temperature, and adjust the air/fuel ratio and ignition timing to meet the specific demands of the engine, at that temperature.