Expansion Valve In Car AC : Symptoms, Location & Replacement Cost

car ac expansion valve

A bad car AC expansion valve can cause the entire air conditioning system to fail. A car’s air conditioning system consists of many parts that play a vital role in the efficient operation of the system. Similarly, these parts have the expansion valve, which expands the compression of the refrigerant as a spray in the air conditioner system and cools the temperature of the refrigerant. This allows adequate amounts of refrigerant to flow smoothly throughout the air conditioning system.

In this article, we will learn about the bad expansion valve in car AC in detail so that you can easily identify any problem related to the AC expansion valve in your vehicle and consider the appropriate solution.

What Is Expansion Valve In Car AC?

A car AC expansion valve is a vital component used in a vehicle’s air conditioner system that controls the flow of refrigerant, allowing the refrigerant to expand and cool faster. By controlling the flow of refrigerant, the expansion valve ensures optimal temperature and pressure, contributing to efficient cooling performance within the vehicle’s air conditioning system. An expansion valve is located on the engine bay side of the evaporator coil and has an AC condenser line connected to it.

The refrigerant expanded and cooled by the expansion valve flows into the evaporator coil, where it absorbs heat from the surrounding air and cools the car cabin. In simple words, the expansion valve helps maintain optimum temperature and humidity levels inside the vehicle cabin by controlling the flow and pressure of the refrigerant.

Car AC Expansion Valve Location

The AC expansion valve in a car is mounted on the evaporator coil, which is usually located inside the dashboard of the car. The evaporator housing contains the evaporator coil, blower fan, and expansion valve. But in some vehicles, the AC expansion valve is also located on the engine bay side, connected to the evaporator coil.

In most cases, accessing and replacing the expansion valve can be a complicated task because it is located inside the dashboard, and removing it often requires disassembling the dashboard and parts of the AC system.

Symptoms Of Bad Car AC Expansion Valve

Symptoms of a faulty car AC expansion valve are poor cooling performance, uneven cooling, or no cooling at all. Additionally, other signs may include the AC compressor running constantly, the AC compressor overheating, excessive frost or ice accumulation on the evaporator coils, irregular temperature fluctuations, and unusual noises.

Let us know these symptoms one by one in detail so that you can know about the bad expansion valve of your vehicle’s air conditioning system and think about its appropriate solution.

1. AC Compressor Continuously Running

When the expansion valve of the car’s AC is damaged or stuck, then the flow of refrigerant compressed by the compressor starts continuously from inside it. Due to this, excessive refrigerant pressure does not build up in the output refrigerant pipeline even when the AC is overcooled, and the high pressure switch is unable to signal the refrigerant pressure reading to the ECM. As a result, the ECM keeps the power supply to the AC compressor on continuously. Due to this, the AC system does not trip, even when there is excessive cooling.

2. AC Compressor Overheating

In an AC compressor, the piston moves continuously to build up the pressure of the refrigerant, which causes the temperature to increase due to friction. But due to the high pressure in the refrigerant pipeline created by the expansion valve to maintain the normal temperature of the AC compressor, the high pressure switch sends a high pressure signal to the ECM and the ECM turns off the power supply to the AC compressor. Due to this, the temperature of the AC compressor remains constant.

But when the expansion valve gets damaged or clogged and the AC compressor runs continuously, the refrigerant pressure increases, causing the AC compressor to get overheated, due to which the piston and rubber seal of the AC compressor can be badly damaged.

3. Frost Build Up On Vents

Whenever the expansion of the AC system is bad or stuck, Then, in that case, the AC compressor runs continuously without any cuts. Due to this, excessively cold refrigerant starts reaching the evaporator coil continuously. And the temperature of the evaporator starts to drop to zero.

Due to which ice starts freezing in the cooling coil. This causes frost to build up on the vents, return suction pipe, and AC compressor if there is a lot of frost accumulation, even in the summer season. So this could be a symptom of a bad expansion valve in the AC system.

4. Warm Air Flow From Vents

A bad expansion valve in the AC system can cause you to feel hot air coming out of the vents. A bad or clogged expansion valve prevents the flow of refrigerant compressed by the AC compressor from going to the evaporator, and the AC compressor starts getting overburdened.

And the high pressure sensor sends a signal of excess refrigerant pressure to the ECM and the ECM turns off the power supply to the AC compressor, due to which you can feel the hot air coming through the vents even when the AC system is on, even if you have set the temperature selector of the AC system to the minimum temperature.

How Do I Know If My AC Expansion Valve is Bad?

If there is inadequate cooling or uneven temperature distribution in the cabin of your vehicle, Additionally, low cooling efficiency, varying temperatures between vents, and possible frost or ice formation on the evaporator coils may indicate a faulty expansion valve. If you notice these symptoms, you need to have the AC expansion valve checked and diagnosed.

Car AC Expansion Valve Replacement Cost

On average, a car AC expansion valve replacement cost can range from $280 to $400. A new car AC expansion valve can cost $170 to $220, and a mechanic’s labor cost to replace it can range from $110 to $180. 

However, this estimated cost may be more or less depending on the vehicle models and the location of the mechanic. The cost of AC expansion valve replacement by an independent mechanic may be slightly less than that of a certified garage mechanic.


Q. What causes an AC expansion valve to fail?

A failing AC expansion valve can result in dirty refrigerant particles, which can block the opening of the expansion valve and the reason for this is also a dirty refrigerant filter and condenser, because many times the pistons of the AC compressor start rubbing. Due to this, its fine particles can go into the expansion valve due to friction.

Q. What does the expansion valve do on a car’s AC?

The expansion valve expands by reducing the high refrigerant fluid pressure by the AC compressor. Due to this, the refrigerant fluid is cooled. The expansion valve is always attached to the evaporator, due to which the refrigerant fluid cools the evaporator.

Q. Can AC work without an expansion valve?

No, the car’s AC system cannot function without the expansion valve. It is an important part of the air conditioning system.

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