Coolant Temperature Sensor

Fig. 12 Water temperature sensor:

The water temperature sensor, incorporated into the thermostat housing, Fig. 12, monitors change in cooling water temperature and transmits a signal for the fuel enrichment to change the pulse duration during warm-up.
The temperature sensing unit employs a thermistor which is very sensitive in the low temperature range.
The electrical resistance of the thermistor decreases in response to the rise in water temperature.