Home Diagnosis and TroubleshootingClimate Control and Air Conditioning Expansion Valve AC Car – How To Diagnose This Problem?

Expansion Valve AC Car – How To Diagnose This Problem?

by Jordan Harris
Expansion Valve AC Car

Are you feeling that your AC system is not working properly and you think that the expansion valve AC car is broken? If this is the case, then you are at the right place because there will be a lot to cover on this topic where we will learn everything you need to know about this expansion valve.

Having a properly working AC system in your car is quite an essential thing these days. It’s not like back in the day when these AC units were a luxury and were only used by the rich. Now they are used by everyone out there.

And before the hot season comes, it is quite essential for you to make sure that your AC system is working properly. Good testing is necessary to perform before the season to make sure everything works. And if it doesn’t and you think that the expansion valve AC is broken, then you are at the right place because there will be a lot to cover on this topic where we will learn everything you need to know.

First, we will start from the basics and learn what is an AC system and how does it work. Then we will cover the expansion valve AC car. We will learn how this valve works in detail. Then we will cover the symptoms of a bad expansion valve in your car AC system and how to diagnose it. Later, we will focus on how to replace it and the cost to replace it. So, if you want to learn more, follow along.

What Is An AC System In A Car?

So, let’s start from the basics and learn more about what the AC system is in general. That will make understanding what expansion valve AC car is and how everything works as a whole unit. Also, not everyone here is quite familiar with this concept so a good introduction is quite essential for everybody. If you feel like you are well prepared, you can just jump on the following chapters if you want. If not, keep up with us for a bit.

Now, what is an AC system? AC system is an abbreviation for air conditioning system. This system is a device that removes the heat and also controls the humidity of the air in the process. All this in an enclosed environment. Which in our case is the car.

Most modern cars have AC systems installed. In the past, these systems were pure luxury and were only included into the top of the line models. But as the years went by, AC systems have become cheaper. And now the AC comes as a standard on 99% of the cars that are produced. Which is quite an insane achievement for 50 years of use.

As you know these systems are using a special gas to achieve this cooling. This gas in the past was known as R-12 or Freon. But since recently this gas was ditched because of the damaging effect on the ozone layer it created and was replaced with the R-134a. A much more sustainable gas that is less harmful.

But we are going to cover that in-depth later in the article. Now let’s focus on how the AC system works in a car and then we will take a look at the expansion valve AC car.

How Does The AC System Work In A Car?

Now let’s cover something important and that is the general idea of how a car AC system works in reality. Knowing this will help you get to the point where this expansion valve sits in and get the perspective of how everything works. First, we will discuss the AC system and then in the following chapter, we are going to focus on the expansion valve AC car and its role. So, follow along.

The AC system is an enclosed circulating system composed of the AC lines, condenser, evaporator, compressor, expansion valve, and other smaller components that make this system.

Everything starts in the AC compressor. This powerful device is doing all the heavy lifting and powers up the AC system. The AC compressor is driven by the drive belt also known as the serpentine belt.

When the AC compressor kicks in all the magic starts to happen. The compressor is compressing the R-134a gas and brings it to boiling temperature and then this compressed gas is sent to the condenser. The condenser is a radiator-like device. This device is cooling down the gas and converts it back to liquid.

Then the liquid goes into the dryer. The dryer is the one that prevents gas to flow further. Meaning that only liquid can pass through.

Then from the dryer, this liquid travels to the expansion valve AC car that we are covering. More on the valve in the following chapter.

And from the expansion valve, the gas travels into the evaporator. And in the evaporator again the liquid is turned into a gas. Next to the evaporator, there is a fan that blows the cold air into the cabin (as you’re trying to figure out how to make car AC colder). After the gas escapes from the evaporator it is sent again to the compressor.

What Is An AC Expansion Valve And How Does It Work?

Since we saw how the AC system works in practice and the whole process of turning the gas into a liquid by the compressor is familiar to us.

Now we can discuss more on the expansion valve AC car. What is this component really and what is its role in reality?

In reality, this component is only a valve that converts the high-pressure liquid into a vapor and liquid mix and also regulates the level of gas that is pushed into the evaporator.

The expansion valve is a valve that opens and closes, this valve has a wire that goes into something known as a sensing bulb. This sensing bulb is an enclosed metallic object that is filled with refrigerant. This sensing bulb is mounted at the end of the evaporator.

So, when the coolant boils inside the sensing bulb, then this boiling gas then goes to the expansion valve. This is basically a message or an electric signal. The sensing bulb sends a message to the expansion valve. Telling it to open the valve and let more refrigerant flow into the evaporator. The gas enters at high-pressure liquid-vapor mix at the start as we mentioned. But when it escapes it is converted into a low-pressure gas.

This conversion is quite an essential process because if there is no conversion and the liquid enters the AC compressor, it will damage it permanently. That’s why the expansion valve AC car is such an important component that keeps the system in check.

Sadly though, this expansion valve is known to break down and cause a number of issues on your vehicle. These are also known as expansion valve AC car symptoms. They indicate that something is wrong with the system. And more on them up next.

Bad Expansion Valve Symptoms

We learned about the expansion valve AC car and we understood that it is an extremely crucial component that allows your AC to function properly. Without it, the AC would not work right and will produce some symptoms that are associated with bad air conditioning.

Expansion Valve AC Car

But what are these symptoms of a bad expansion valve AC car? Let’s elaborate on them in the following chapters and learn more about the possible symptoms caused by the faulty expansion valve.

1. AC Blows Warm Air

Now let’s cover the first symptom of the expansion valve AC car. And that is when the AC blows warm air all the time. Why is this the case? You adjusted the AC to blow cold but it’s blowing warm air (and want to figure out how to make AC colder in car)?

A little bit of warm air is completely normal at the start when you turn on the AC. But if the AC keeps blowing warm air after 5 or 10 minutes then something is really wrong with the system. Either there is no or little refrigerant in the system or the expansion valve AC car is broken. And the most probable reason is the first one.


But still, the expansion valve can cause this problem in your car. What is important for you to do in this situation is not to overload the system and just turn it off. By doing this, you will prevent any possible damage to the AC compressor. Then you can check the expansion valve and check its condition. If you are not experienced, you can just take the car to a shop and let them do the work for you. Now let’s move on to the next symptom of expansion valve AC car.

2. Poor AC System Performance

Another symptom associated with this problem of bad expansion valve AC car is the poor overall AC work. But what does this means?

This means that the AC will be very inconsistent and will not deliver good enough performance. If the expansion valve doesn’t open when needed it will not allow refrigerant to enter the evaporator and cool the cabin down.

When this happens, you will notice how the AC simply blows cold air but suddenly the air becomes hotter and again it blows cool air. This work is inconsistent and will not do any good to you and your experience while you are driving the car.

The important thing when this happens is to turn off the AC. By doing this you will somewhat be safe from problems. Meaning that the problems that this expansion valve AC car is making will not become worse and ruin the AC compressor. Compressors are really expensive and if the valve is not converting the liquid into a gas and the liquid enters the compressor, it is going to destroy it.

So, beware of this and make sure that you play it safe when it comes to this stuff. You don’t want to pay a whole fortune for a compressor because the expansion valve AC car was broken and you didn’t react on time. Now let’s move to the next symptom.

3. Frost Is Forming On The AC Lines And Evaporator

Another symptom of a bad expansion valve AC car is the frost that builds up on the AC lines and also on the evaporator.

If you notice something like this, then you should react quickly. It is not a normal situation to see frost development on the lines and also on the evaporator.

This frost can be hard to see. Especially for the untrained eye that is not familiar with the AC system and doesn’t know where these lines are going. So, it is useful to check a few diagrams online for your car and understand the plumbing of the AC system specific to your model.

This way, you will be able to tell if your AC lines are frosty and are developing some ice on them. If they are, there might be something wrong with the expansion valve. It either releases too much gas into the evaporator or it is blocked and ice is forming on this valve specifically. Either way, not a good situation because you can overload your AC compressor. And that’s what we are going to cover in the following chapter.

4. AC Compressor Constantly Working And Is Overloaded

Another symptom of a bad expansion valve AC car is when the AC compressor is constantly under heavy load and is working like there is no tomorrow.

This shouldn’t be the case since the AC is a unit that turns on and works at idle speeds all the time. But if the expansion valve AC car is releasing too much gas than it should into the evaporator, the gas will flow at a much higher pace and the AC will not be able to meet this speed.

So, the compressor will be put under a lot of stress that could possibly damage itself. That’s why whenever you notice too much frost on the evaporator and the lines. Then the compressor is probably overworked and you should turn it off.

Then start it again and see if the situation has been resolved. If not, just take your car to your local shop that is working with AC systems and tell them how the system is behaving and tell them to check the expansion valve AC car. Then based on their input, you will see what will be your next steps.

5. AC System Failure

And the last symptom concerning the expansion valve AC car is the complete AC system failure. The system will eventually fail if you keep running the car with a bad expansion valve.

There could be refrigerant leaks developing and also some of the lines could fail completely and let all the refrigerant leak out.

The AC compressor is one of the most sensitive components when it comes to this stuff and if this component fails, you are going to pay big money to fix it. A new compressor for some cars could easily cost a grand or more in some cases, which is a rather insane amount of money.

That’s why you need to diagnose the bad expansion valve AC car and sort this problem as soon as possible. In the following chapter, we are going to cover precisely where we will learn how to diagnose this problem. So, stay on.

How To Diagnose Bad Expansion Valve?

Diagnosing a bad expansion valve AC car can be a really tricky job. Since not a lot of people can do it. For this to be possible, you need to have some prior experience with working with AC systems.

Namely, you need to understand the cold and hot sides and work with the gauges. Then you need to learn how to properly read these gauges and learn if there is an obstruction and where it is.

And diagnosing a thing like this is not something simple thing. Remember that this system is full of refrigerant and this refrigerant is toxic if you are exposed to it. Especially if it’s on the hot side when there is so much pressure going on.

That’s why maybe it is best to leave this job to professionals and let them sort this thing out quickly and effectively. We attached a video where you could see this diagnosing procedure in depth.

Also, if you are sure that the expansion valve AC car is bad, then you can just go ahead and replace it. If you had experience and you charged your AC system before, then this should be an easy job for you. In the following chapter, we are going to explain how this is done on a car. So, stay on.

How To Replace A Car’s Expansion Valve AC?

Now, how you can replace the expansion valve AC car? Let me tell you first that this is not one of the simplest things that you can do on your car. It is very labor-intensive and requires a lot of patience and skill to get it sorted out since the expansion valve is mounted on the evaporator which is located under the front dash. So, getting there will be a real pain.

But if you are decisive, then you can do it. The first thing you will need to do is to get a new expansion valve for your car. Make sure that you get the correct part and not get something else.

Then you will have to drain the AC system from the refrigerant. You just don’t want to hurt yourself. Make sure that the system is properly drained from the refrigerant.

Then you will need to find the evaporator, for this, you will have to remove two bolts from the side of the engine. Then you will need to remove the glove compartment and then reach the evaporator.

And even then you will have access to remove the expansion valve AC car and replace it. Then you will need a vacuum machine to make sure that the system is clean and then fill it up with refrigerant. All this process is extremely labor extensive and not easy for a beginner to do. So, if you are a beginner, you might want to start with something easier than the expansion valve AC car.

Cost To Replace A Car’s Expansion Valve AC?

So, we learned how to replace the expansion valve AC car, now let’s see what is the cost to replace this valve? And sadly, the cost to replace it is not that cheap.

Mostly because of the position where this valve is located and that is under the front dash. So, getting there could be a bit of a pain. This is why a lot of shops will charge you some money for this work.

If you get it sorted for less than $400, you can consider yourself lucky. The part itself is relatively inexpensive but the labor is very demanding with this job. The more complex the car, the more difficult is to reach this evaporator.

Expansion Valve AC Car

If you have a pickup or an older car from the ’90s or earlier model, this work will not be that difficult and expensive since everything is there and easily swappable. If you have some modern exotic car, you can even pay up to $700 for this work, which is crazy money for an expansion valve AC car. But that’s how things go.

If you replace it by yourself, you can pay less than $100. For the parts and also for the refrigerant that you will have to recharge the AC system after you are done. Not to forget also the discharging of the refrigerant. So, the overall cost could be up to $150 if you do it the DIY way.

Conclusion To A Car’s Expansion Valve AC

In this article, we have covered quite a bit when it comes to expansion valve AC car. We learned how the AC system works and from what components is this system consists. Then we covered how the expansion valve AC car works and what is its method of action.

After we discussed the symptoms of a bad expansion valve. And there were a few of them as we noted. Then the problem with a warm air blowing as well as the inconsistency and the big load on the compressor. Lastly, we learned how to diagnose and replace the expansion valve AC car and also we covered the cost for all this work.

You may also like

Leave a Comment