What is the Evaporator Temperature Sensor (Switch) all about?

The air conditioning in your car operates by circulating refrigerant to remove heat and moisture from the air entering your passenger compartment and dissipating it into the outside air. The refrigerant that passes through the evaporator inside your car is metered by the expansion valve so the set amount of cooling can occur 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 mounted on the evaporator or in the evaporator housing to monitor the evaporator temperature. It prevents 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 introduce 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.

Keep in mind:

• Air conditioning systems are filled with refrigerants that require professional recovery and disposal.

How it's done:

• The evaporator temperature sensor is verified and needs to be replaced
• The defective evaporator temperature sensor is removed from dash evaporator case
• The new evaporator temperature sensor is installed and dash reinstalled
• The a/c is recharged
• The vehicle is road tested for proper operation and a/c operation checked

Our recommendation:

The evaporator temperature sensor only requires replacement when it fails. But if the evaporator is being replaced it is advisable to change the temperature sensor at the same time. If it is determined that the evaporator temperature switch or sensor is not working as it should, it will need to be replaced by one of our expert mechanics.

What common symptoms indicate you may need to replace 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

How important is 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 replaced as it suits you.