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Your car’s air conditioning (A/C) system is made up of a variety of components, one of which is an expansion valve (or an orifice tube). Like any other part of the A/C system, the expansion valve can prevent proper cooling of the cabin when it fails.

Naturally, when you’re A/C isn’t cooling well due to a bad expansion valve, your car can be extremely uncomfortable, which means you’ll want to fix the problem right away.

car ac system
The expansion valve can prevent proper cooling of the cabin when it fails.

What Does an Expansion Valve Do?

To understand the role of the expansion valve, it helps first to have some knowledge of how the A/C system works. All automotive A/C systems use refrigerant as a heat transfer mechanism to remove heat from the cabin. The process starts at a device called the compressor.

When the engine is running and the A/C is engaged, the compressor pressurizes and distributes vapor refrigerant into the system. After leaving the compressor, the refrigerant enters a radiator-type device, called the condenser, which transfers some of the heat from the refrigerant into the atmosphere. The refrigerant also turns into a liquid while inside the condenser.

Next, the high-pressure liquid refrigerant enters a restriction. The restriction lowers the pressure of the refrigerant and meters it into the next part of the system—the evaporator core (another radiator-type device).

Depending on the system design, the restriction will be either an orifice tube or an expansion valve. If an expansion valve is used, a diaphragm within the valve works with a temperature-sensing mechanism to regulate the rate at which refrigerant enters the evaporator core.

From there, a blower motor then forces air through the evaporator core, causing heat from the cabin air to be transferred to the refrigerant. At the same time, the refrigerant boils and turns into a low-pressure vapor, then heads back to the compressor to restart the cycle.

Another thing to mention is that all A/C systems have a drier that removes moisture from the lines. Systems that have an expansion valve use a receiver-drier, whereas those with an orifice tube rely on an accumulator-drier.

automative expansion valve
Expect to pay somewhere between $150 and $400 if you want to have a mechanic replace your expansion valve.

Symptoms of a Bad Expansion Valve

Over time, your car’s expansion valve (if it has one) can eventually fail, resulting in at least one  of the following symptoms:

Air Conditioning Blows Warm Air

The expansion valve is just one of many problems that can cause your car’s A/C system to blow nothing but warm air. If the valve is stuck closed, refrigerant flow to the evaporator core will be restricted, preventing the A/C system from working as it should. Meanwhile, if the valve is stuck open, the evaporator core will be flooded, preventing proper A/C system operation.

Refrigerant Oil and/or Dye Buildup

It’s possible for the expansion valve to develop leaks. When that happens, you may notice refrigerant oil accumulated around the valve. You may also notice green dye if there has been dye added to the system at some point.

Frost Accumulation

An expansion valve that’s stuck open can result in a flooded evaporator core, which can cause frost to accumulate at the evaporator’s outlet. On the other hand, frost buildup on the outside of the expansion valve can indicate the valve is clogged or stuck closed.

Expansion Valve Replacement Cost

Exactly how much it costs to replace an expansion valve will depend on several factors, including what type of vehicle you have. If you choose to have a professional replace the valve, you can usually expect to pay somewhere between $150 and $400 to get the job done. Because the A/C system must be evacuated and recharged when the valve is replaced, most of the repair cost comes from labor.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic.

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