3 Reasons You May Have a Bad Air Conditioner Expansion Valve

An AC unit installed outdoors beside a building.

The expansion valve in a heating and cooling system acts as a cut-off valve. If the expansion valve is damaged, the unit may no longer turn off once it reaches temperatures that will normally cause it to switch off. The article that follows will share with you common problems your heating or cooling unit may have that can be caused by a faulty expansion valve.

Note: Expansion valves exist in all AC systems, even in your vehicle. Symptoms of a car's expansion valve malfunctioning won’t be quite the same as the ones listed here, but since the purpose of the valve is the same in both cases, it shouldn't be difficult for you to figure out if the valve is bad in your car.

1. Frozen Coils

The air conditioning unit works on the premise of pushing liquid through metal coils. This liquid is super cooled and a fan blows air through the system. The air blows over the metal coils and then finds its way out of the vent and into your home to lower the air temperature. An expansion valve helps to regulate the operation of the system. If the expansion valve is faulty, the flow will not cut off and the coils will freeze.

2. Continuous Running

An air conditioner has several internal devices which detect the temperature inside the unit and outside the unit. The unit will automatically turn off once a certain temperature is reached. So, if the unit never turns off, something has to be malfunctioning in the unit’s temperature detection, which could mean a broken expansion valve.

3. Odd Noises

A failing expansion valve will cause several distinct noises. Noises can indicate the potential for other problems, but clanging, banging, and squealing are some of the regular noises associated with a bad expansion valve. If you hear anything strange from your AC unit, it is best to call the professionals for a look.

Fortunately a bad expansion valve is a relatively inexpensive fix, depending on the technician who services it, so you should never hesitate to call immediately if you suspect a problem. Running an AC unit with a bad expansion valve will end up costing you far more in cooling bills than repair costs if you get it done quickly, and by waiting, you could be putting other parts in your unit at risk for damage.