Evaporator Temperature Sensor / Switch: Description and Operation

The A/C thermostat is located on the evaporator housing. The A/C thermostat turns OFF the A/C compressor clutch if the temperature at the evaporator goes below 3°C (37°F). This prevents condensation from freezing on the evaporator fins and blocking the air delivery into the passenger compartment. The blower motor will keep running when the sensor turns OFF the compressor. If the temperature goes below 3°C (37°F), the A/C thermostat goes OFF, removing ground from the condenser fan relay. This deenergizes the relay, removing voltage from the condenser fan motor, and the fan stops running.