Car A/C Evaporator Sensor

By 29 August 2014

An evaporator sensor is used on a system which generally uses electronic control as opposed to electrical control. These systems use the temperature sensor to feed a voltage reading to a control module which is programmed to use the data and compare it to stored data in its memory. The sensor is generally an NTC type sensor which means it has a negative temperature coefficient. This means that with an increase in temperature the resistance of the sensor will reduce. This will affect the current flowing through the sensor and the voltage across the sensor. The module can apply this data and when the corresponding voltage is sensed, associated with 1°C, the module will disengage the compressor clutch via a relay to stop the evaporator from freezing. The compressor clutch will be re-engaged when the temperature of the evaporator reaches 2.5°C.The sensor is generally fitted to the evaporator fins for direct measurement. Advanced vehicle electronic systems may use a multiplex wiring system to transfer the information digitally.