Car A/C De-ice Switch

By 27 August 2014

A de-ice switch (Fig. 2.45) is a temperature sensor and relay built as one unit.The temperature sensor is fitted to the evaporator’s fins and measures the temperature of the evaporator surface using an NTC type temperature sensitive resistor.This sensor sends the information to the relay in the form of a voltage drop and when approaching the freezing point of water (0°C) the current to the compressor clutch is interrupted to increase the pressure in the evaporator and avoid the surface water freezing.With a system threshold of 1°C at the surface, the relay will turn the compressor off. Once the surface increases to 2.5°C, the compressor, via the relay, will be switched on again.