Maintenance Tips, Tricks And Hacks For Your Vehicle

7 Reasons Why Your Car AC Is Not Working And How To Fix It




Having a non-working AC in the middle of the summer can be pretty frustrating, but also expensive.

Key Takeaway

  • A car’s air conditioning system works by compressing a refrigerant that absorbs heat from the car’s interior when it evaporates, then condensing it outside the vehicle to release the heat, and finally sending the cooled air into the car through the vents.
  • Your car AC may not be working if the refrigerant is leaking, the AC condenser is blocked/broken, if there are electrical issues, a faulty AC cooling fan, a faulty AC accumulator filter drier, a faulty compressor, or a faulty evaporator.

How Does The AC Work

7 Reasons Why Your Car AC Is Not Working And How To Fix It

In order to understand your car’s AC system, you have to start with the refrigerant. The refrigerant is a chemical used in the AC system.

When it is in a gas state, it is able to collect, absorb and hold heat. When it is converted into a liquid state, it releases that heat, and that process repeats over and over again.

That is how the AC works. In order for this process to happen, the pressure has to be right and all the components have to work properly.

There are 5 major AC system components:

  1. Compressor and clutch
  2. Condenser
  3. Expansion valve
  4. Evaporator
  5. Accumulator filter drier

All of the components are connected by hoses.

A compressor pumps the refrigerant under pressure throughout the AC system. After leaving the compressor, the refrigerator enters the condenser before it is transferred to the cabin.

The expansion valve transfers the refrigerant into a cold gas. From there, the cold gas passes through an evaporator and absorbs the heat from inside the vehicle.

At the same time, a fan blows across the fins of the evaporator chilling the air that goes into the passenger cabin. The refrigerant then passes through a drier to filter out any moisture before returning to the compressor to begin the process again.

7 Reasons Why Your Car AC Is Not Working And How To Fix It

7 Reasons Why Your Car AC Is Not Working And How To Fix It

Here are the most common reasons why your car AC is not working:

1. The AC is leaking refrigerant

A common problem with car air conditioners can be a leakage of refrigerant. This means that not only are you likely to feel an uncomfortable warmth radiating from the vents, but your AC system may also be losing vital components.

While it might just seem like an inconvenience, low levels of refrigerant can drastically reduce the efficiency and life span of your vehicle’s air conditioning system.

It’s actually very easy to find if your AC is leaking refrigerant. Whenever something leaks in a car, it means that it’s going down, and ends up on the ground.

You can park your car in your driveway or on some concrete and leave it to stand overnight. In the morning, back up the car a little bit and see if there is fluid on the ground.

If there is, you can perform a small test like smelling the fluid. If it smells like oil, then it’s oil. However, If not, if it has that freon/refrigerant smell, you got yourself a leaky AC.

If you don’t want to wait 24 hours and you want to diagnose and fix your AC right away, you can perform another test. You can add a special dye to the AC system.

But the dye is very difficult to see, so you will need UV light. Start your car and your AC. Add the dye to the AC system.

Grab your UV light and carefully light all the pipes that go in/out of the AC system. It’s best if your car is parked in a garage and the light is off.

If you are able to find where the leaking is coming from, mark that place and go to the mechanic. Or, if the area is very small, you can try taping it with heat-resistant tape says AutoZone.

Cost of repairing AC with leaking refrigerant

Repairing a car AC with leaking refrigerant may cost you anywhere from $150-$800. To have a technician inspect your AC, and check all the hoses and connections will cost $100-$300.

Recharging your AC can cost around $160. Changing some parts on your AC has an average cost of $488. You can save up some money by fixing it yourself.

Make sure you have the required tools before starting your work.

Repair It Yourself

In the best scenario, you can use a commercial product to stop the leaking. These products say that they will fix leaks in condensers, evaporators, hoses, and gaskets.

The products go for around $25. If this doesn’t work, take your car to the mechanic.

2. The AC condenser is blocked/broken

This is a very common issue, and the symptoms are pretty clear. The mission of the AC condenser is very important and can be found in all car AC systems.

The condenser is converting the refrigerant coming from the compressor. The refrigerant comes with a high temperature and high pressure and then it’s converted into a high-pressure liquid and cooled thanks to the condenser.

If your car AC is working, but it’s not cooling as it used to, you might be looking at a blocked/damaged condenser. If the air cannot flow freely, the cabin cannot be cooled properly.

A blocked/broken condenser can cause a leak. Every part has a lifespan, and so does the condenser. When a condenser leaks, it is a noticeable leak and you have to replace the whole condenser because it is a one-piece part.

Cost of repairing a blocked/broken AC condenser

You won’t be happy when I tell you what is the average cost to replace the condenser. The labor cost for repairing a blocked/broken AC condenser can range anywhere from $160-$300.

The condenser itself is from $240-$350. So, you are looking at an average cost of $500. It’s not that cheap, but, I cannot imagine a summer without an AC. 

You can save up some money by fixing it yourself. Make sure you have the required tools before starting your work.

Repair the blocked/broken AC condenser yourself

This fix will require some tools that not everyone has at their home.

  1. First, start off by recovering the refrigerant. For this, you need a machine. They cost anywhere from $300-$600. It will be cheaper if you just leak the refrigerator.
  2. Remove all parts(radiator, condenser fans, grills, headlights) that are in the way of the condenser.
  3. Remove the AC lines that lead to the condenser.
  4. Disconnect the condenser. Loosen up the bolts that hold the condenser. Remove it slowly and make sure you don’t damage the wiring.
  5. Install the new condenser.
  6. Reinstall the lines leading to the condenser.
  7. Recharge the AC with refrigerant.

3. AC electrical issues

These electrical issues are not as common as refrigerant leaks, but they still happen. Performing a visual inspection is a great start. The car AC has many switches and relays, and many parts mean more chances to break down.

Non-operating AC does not mean that the AC itself is broken, or a condenser or a fan. It can be the little things.

There are low-pressure and high-pressure cut-off switches, power steering switches, and wide-open throttle switches. These components’ mission is to disengage the compressor while it loads. If your car AC turns on and starts to blow hot air, it could be because of the components that I mentioned above.

Another thing that fails, and is an electrically operated component is the compressor clutch. This is a separate part from the compressor and can be serviced separately.

This component is energized by a coil that pulls the clutch into a grip. This component connects the engine revolutions and a freon pump.

The compressor clutch can be checked and diagnosed with an ohmmeter. Replacing the compressor clutch can be a delicate operation.

Cost of repairing AC electrical issues

  • The low-pressure and high-pressure cut-off switch costs around $15-$30.
  • The power steering switch costs around $25-$30.
  • And the wide-open throttle switch costs $13-$20.
  • The compressor clutch is a little expensive. It costs anywhere from $150-$300.
  • The labor costs $80-$200.

Repair It Yourself

I personally do not try to fix any electrical issues on a vehicle. If you don’t know what you are doing, it is best if you pay a mechanic.

A small error with the electronics can lead to damage. Anything from a blown fuse to setting your car on fire can happen.

4. Faulty AC cooling fans

As I said before, the condenser converts the refrigerant to liquid form. This means that the condenser has a lot of work and gets hot.

This is where the AC cooling fan comes into play. This component is designed to keep the condenser cool.

Here are a few symptoms that a faulty AC cooling fan has:

  1. If you feel lukewarm air coming out of the air vents, that is the first symptom of a faulty ac cooling fan. This happens when the fan is not working and the condenser has gotten very hot.
  2. If your car overheats while idling can also be a symptom of faulty cooling fans. During the converting process, the condenser can create a big amount of hot air. This hot air gets to the engine and affects its temperature. This issue occurs only when your car is parked. Once you get the car moving, it will cool down from the airflow.
  3. Another symptom is a burning smell coming out of the AC vents when your turn on the AC. This happens when the condenser overheats to a burning point and emits an odor. The more you drive your car with an overheated compressor, the more damage is done. So, whenever you feel a burning smell, turn off the AC and fix your issue.

Cost of repairing faulty AC cooling fans

The cost of a Fan can vary from $307-$784. Fans of BMW are the most expensive on the market. The other cars use fans with a price of $307-$440.

The labor cost is anywhere from $70-$238. Again, the BMW replacement is the most expensive. You can save up some money by fixing it yourself. Make sure you have the required tools before starting your work.

Repair the faulty AC cooling fans yourself

  1. Start the car engine and open the hood. Locate the condenser fan.
  2. Test the condenser fan relay which is located in the relay box under the hood.
  3. Check the pressure of the AC system. There is a general reading located in the manual of each car.
  4. Remove the condenser by removing the electrical connections and then remove the mounting bolts.
  5. Install the new condenser.
  6. Test the AC to make sure it is working properly.

5. Faulty AC accumulator filter drier

This component acts as a filter for the car AC system. It is filled with a moisture-absorbing material.

It is filtering the debris that may get inside the AC system and it absorbs the moisture that gets pumped into the AC system.

If this component fails, you are looking at corrosion or leaks. A faulty ac accumulator filter drier can be diagnosed with these symptoms:

– If you hear a rattling noise when you turn your AC on could be because of the accumulator. The accumulator has chambers inside, and that noise could be because of internal damage(corrosion).

– If your ac is leaking refrigerant it could be because of the accumulator. If you notice a huge pool of refrigerant in the morning, you must act fast or all of your refrigerant will leak out.

– The moldy smell. I hate this symptom. This actually happened to me when I was on vacation and I couldn’t change the accumulator right away because I was in a different country. I will never forget that moldy smell.

Cost of repairing a faulty AC accumulator filter drier

The AC accumulator has a price range of $41-$103. The labor cost goes from $70-$126. You can save up some money by fixing it yourself. Make sure you have the required tools before starting your work.

Repair the faulty AC accumulator filter drier yourself

This is also a complicated process.

  1. Store the refrigerant by using a recovery machine.
  2. Remove the evaporator tube nut.
  3. Disconnect all electrical connections from the AC.
  4. Remove the compressor hose, accumulator, and retaining bracket bolt.
  5. Remove the O-ring seals.
  6. Lubricate and install new O-rings.
  7. Install the compressor hose, accumulator, and retaining bracket bolt.
  8. Connect the electrical connections to the AC.
  9. Recharge the AC system.
  10. Test the AC.

6. Faulty car AC compressor

This is a component that you don’t want to fail. Not only will it disable your AC, but it will bring you a huge invoice to pay.

This is the most important component of a car AC system. When it starts to fail, it will show a couple of warning signs:

– When you turn on the AC, you will not get cold air blowing. As a matter of fact, it will be as same as if you never turned the AC on.

– Very loud noises coming from the compressor. All kinds of noises can be produced from the internal bearings or seized. These small components are not something that you can replace. You will have to replace the entire compressor.

– When the clutch is not moving. This part is what turns them on and off the compressor. If this component fails, it can leave the compressor turned on for a longer period of time, and again, you will have to replace the entire compressor.

Cost of repairing a faulty AC compressor

As I said before, this is not something that you want to fix. It is very expensive.

The compressor can cost from $509-$3188. The labor is anywhere from $322-$805. You can save up some money by fixing it yourself. Make sure you have the required tools before starting your work.

Repair the faulty AC compressor yourself

  1. Check the pressure.
  2. Check the power and ground of the compressor.
  3. If found faulty, remove all the refrigerant using a machine.
  4. Remove the compressor, receiver drier, orifice tube, and expansion valve.
  5. Install the new compressor and the remaining parts(receiver drier, orifice tube).
  6. Recharge the AC system.
  7. Test it.

7. Faulty AC evaporator

This part regulates the AC temperature. Any damage to this component may disrupt the cooling process. This component usually starts to leak refrigerant when it gets damaged.

The most common reason why it gets damaged is by debris that gets through the air intake.

– If there is no cold air coming out of the AC, it could be because of the evaporator. If the evaporator switch fails, it can affect the AC system.

– When the temperature changes from cold to hot. This can happen if the evaporator sensor sends an incorrect signal to the computer.

– A faulty evaporator could lead to the AC compressor not turning on. The evaporator temp sensor has an important role. A simple malfunction with the evaporator can disrupt the overall performance of the AC.

Cost of repairing a faulty AC evaporator

Compared to the other parts, I can say that this part is inexpensive.

The evaporator costs anywhere from $144-$164. The labor cost is $126-$168. You can save up some money by fixing it yourself. Make sure you have the required tools before starting your work.

Repair the faulty AC evaporator yourself

  1. Store the refrigerant with a recovery machine.
  2. Cut the joint caps and disconnect the receiver lines.
  3. Tape the lines to avoid debris from entering.
  4. Clean the joints and all areas.
  5. Remove the blower unit.
  6. Disconnect the evaporator temperature sensor.
  7. Pull out the evaporator.
  8. Install the new evaporator.
  9. Connect all the lines.
  10. Test the AC.

Before you start working on your AC, make sure you have the required knowledge and tools to perform the task to the end. Do not start and realize in the middle of the repair that you are missing some of the essential tools.

Make sure that you are very careful when working on the AC. As I said before, there are some parts that are very expensive.

You do not want to risk damaging the AC compressor. If you have basic knowledge of cars, you can at least diagnose the issue and then go to the mechanic.

This way your mechanic won’t lie to you and perform tests that are necessary but costly.


Why is my car AC not blowing cold?

There could be several reasons why your car’s AC isn’t blowing cold air:

Refrigerant Leak: This is one of the most common causes. The refrigerant is what cools the air in the system. If there’s a leak anywhere in the AC system, you’ll likely notice the air isn’t as cold as it should be.

Faulty Compressor: The compressor is the heart of your car’s AC system. It circulates the refrigerant and maintains its pressure. If the compressor is faulty, the refrigerant won’t circulate properly, leading to warm air blowing out.

Clogged Condenser: The condenser’s job is to cool the hot refrigerant after it’s been compressed. If it’s clogged with dirt, leaves, or debris, it won’t be able to do this effectively, resulting in less cool air.

Electrical Issues: If there’s an issue with the wiring, relays, or fuses related to your AC system, it can prevent the system from functioning correctly.

Broken Cooling Fans: Cooling fans help keep the condenser temperature down. If they’re not functioning properly, the system can overheat and not cool the air effectively.

Why is my car AC blowing hot air?

If your car’s AC is blowing hot air, a common culprit might be low refrigerant levels. The refrigerant is the lifeblood of your car’s air conditioning system. It’s responsible for absorbing and removing heat from your car’s interior.

Why is my AC running but not cooling?

If your AC is running but not cooling, it could be due to a dirty or clogged air filter. The air filter in your AC unit plays a crucial role in its operation. It traps dust, pollen, and other airborne particles that can harm your system’s components.

How do I know if my AC compressor is bad?

One clear symptom that your AC compressor might be failing is if the AC is blowing warm or room-temperature air instead of cold air.

The AC compressor is the heart of your air conditioning system, compressing the refrigerant and circulating it through the system. When it’s working properly, it helps in cooling down the air that comes out of your AC vents.

However, if the compressor is malfunctioning or damaged, it’s unable to perform this essential task efficiently. As a result, the AC system cannot cool the air effectively, leading to warm or room-temperature air being blown out.

In Conclusion

In conclusion, there are several reasons why your car AC may not be working, ranging from simple issues like a broken switch or a blown fuse to more complex problems like a faulty compressor or a refrigerant leak.

Understanding these potential causes is the first step toward resolving the issue. While some fixes can be done at home with basic tools, others require professional attention.

Regardless of the complexity, addressing these issues promptly can save you from discomfort during hot weather and potentially prevent more serious damage to your car’s AC system.

So, if your car AC isn’t working, don’t sweat it – identify the issue and take the necessary steps to fix it.



Vide Polowenski, Senior Mechanic

The information in this article is current and up-to-date in accordance with the latest mechanic SOPs.

Please take the time to leave a comment if this article has helped you in any way, you need additional help, or you have a suggestion.

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