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Common Failures Of A Defective Expansion Valve: Symptoms!

Your car’s air conditioning (A/C) system is made up of a number of components, one of which is an expansion valve (or orifice tube). Like any other part of the A/C system, the expansion valve can prevent adequate cabin cooling when it fails. So that you are prevented from this type of inconvenience, we recommend that you learn about the common failures of a defective expansion valve .

Naturally, when your air conditioner doesn’t cool well due to a faulty expansion valve, your car can be extremely uncomfortable, which means you’ll want to fix the problem right away.

What does an expansion valve do?

To understand the function of the expansion valve, one must first know how the air conditioning system works. All automotive A/C systems use refrigerant as a heat transfer mechanism to remove heat from the cabin. The process begins in a device called a compressor.

When the engine is running and the air conditioning is on, the compressor pressurizes and distributes refrigerant vapor in the system. After leaving the compressor, the refrigerant enters a radiator-like device, called a condenser, which transfers some of the heat from the refrigerant to the atmosphere. The refrigerant also becomes a liquid while it is inside the condenser.

The high pressure liquid refrigerant then enters a restriction . The restriction reduces the pressure of the refrigerant and leads it to the next part of the system: the evaporator core (another radiator-like device).

Depending on the system design, the restriction will either be 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 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 returns to the compressor to restart the cycle.

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

Symptoms and failures of a faulty expansion valve

Over time, your car’s expansion valve (if it has one) can eventually fail, leading to at least one of the following common failures of a bad expansion valve:

1. Air conditioning blows hot air

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

2. Refrigerant oil and/or dye buildup

Expansion valve may develop leaks. When this occurs, you may notice refrigerant oil pooling around the valve. You may also notice green tint if dye has been added to the system at some point.

3. Frost buildup

A stuck open expansion valve can cause the evaporator core to flood , which can cause frost to build up on the evaporator outlet. On the other hand, frost buildup on the outside of the expansion valve may indicate that the valve is clogged or stuck.

4. Expansion valve replacement cost

The exact cost of replacing an expansion valve will depend on several factors, including the type of vehicle you have. If you decide to have the valve replaced by a professional, you can typically expect to pay anywhere from $150 to $400 to have the job done. Because the air conditioning system must be evacuated and recharged when the valve is replaced, most of the cost of the repair comes from labor.

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