What to know about the Evaporator Temperature Sensor (Switch):
The air conditioning in your car works by circulating refrigerant to drive away heat and moisture from the air entering your passenger compartment and dissipating it into the outside air. The refrigerant that goes through the evaporator inside your car is metered by the expansion valve so the set amount of cooling can happen without the evaporator freezing up. As air passes through the evaporator core, the refrigerant in the evaporator absorbs the heat and carries it out of the car.
The evaporator temperature sensor is fixed on the evaporator or in the evaporator housing to monitor the evaporator temperature. It stops the air conditioning refrigerant from becoming too cold and having frost form on the evaporator core. If the evaporator sensor fails or starts to read incorrectly, the expansion valve can bring in too much or too little refrigerant into the evaporator. This can cause insufficient cooling due to a lack of refrigerant flow or frost formation on the evaporator.
Facts to Note:
Air conditioning systems are filled with refrigerants that need professional recovery and disposal.
How to Fix:
The evaporator temperature sensor is confirmed and needs to be changed
The faulty evaporator temperature sensor is taken out from dash evaporator case
The new evaporator temperature sensor is fixed and dash reinstalled
The a/c is recharged
The vehicle is road tested for correct operation and a/c operation checked
The evaporator temperature sensor only needs replacement when it fails. But if the evaporator is being changed it is advisable to replace the temperature sensor too. If it is determined that the evaporator temperature switch or sensor is not working as it should, it will need to be changed by one of your expert mechanics.
Common symptoms indicating you may need to change the Evaporator Temperature Sensor (Switch):
No flow through the evaporator when the air conditioning is turned on due to frost
Temperature of the air that flows through the vents when the A/C is on fluctuates
Importance of this service:
Although air conditioning draws moisture out of the air to clear your windows in humid weather, it is more of a convenience feature than a safety feature. Have the air conditioning evaporator temperature switch changed as it suits you.