Why Is My AC in My Car Blowing Hot Air? 9 Common Causes

Worrying why is my ac in my car blowing hot air? Nothing is more irritating than starting the vehicle on a summer day and getting hot air. If the air conditioner is working well, you enjoy going for a ride. But it may be a nightmare since a hot vehicle can rapidly hit 140-degree temperatures or more when it breaks down. It can be a frustrating experience, especially if you do not know why it is happening.

There are several possible reasons why your car’s air conditioner is blowing hot air. We will discuss the most common causes to help you rule out potential causes and get your AC system working fine again.

The Car AC System Explained

Before we dive in, let’s briefly review how the air conditioner system works in a car. The air conditioner is a closed system that has refrigerant circulating through it. The refrigerant helps to cool and dehumidify the air inside your car.

There are several key components in the AC system:


The compressor is the heart of the air conditioning system. It pressurizes the refrigerant and circulates it through the AC system. The compressor is driven by a belt that is connected to the engine. When the compressor is working correctly, you should be able to feel warm air coming from the front of your car.


The condenser is a large radiator located in front of the vehicle. The condensed refrigerant from the compressor goes through the condenser. The hot air from the engine helps to cool the refrigerant as it passes through the condenser.


The receiver/dryer is a canister that stores the refrigerant. The receiver/dryer helps to remove any moisture from the refrigerant.

➨Expansion Valve/Orifice Tube

The expansion valve or orifice tube is a small device that regulates refrigerant flow into the evaporator.


The evaporator is located in the dash of the car and is the component that cools the air inside the vehicle. The refrigerant from the expansion valve goes into the evaporator. As the refrigerant passes through the evaporator, it absorbs heat from the air inside the car. This cooled air is then circulated through the vehicle by the blower motor.

You should familiarize yourself with the main components of the AC system to understand how it works. It will be helpful when troubleshooting why your car’s air conditioner is blowing hot air.

Common Causes of AC in My Car Blowing Hot Air

Why Is My AC in My Car Blowing Hot Air

If you’re constantly asking yourself, “Why is my AC blowing hot air?” it’s time to dig further into the problem. As there could be an underlying issue, here are a few reasons why your car’s air conditioner could be blowing hot air:

❗Leaks in the Refrigerant 

One potential reason why your car’s air conditioner could be blowing hot air is because of leaks in the refrigerant. The AC system is a closed system, so if there are any leaks, it will cause the refrigerant level to drop. A drop in the refrigerant level will prevent the AC system from working properly.

If you suspect there is a refrigerant leak, the best thing to do is take your car to a mechanic so they can properly check and repair any leaks.

❗Electrical System Malfunctions 

Your car could generate hot air due to an electrical problem if all A/C systems are in working order. A broken fuse or damaged wire might cause an otherwise functional air conditioner to stop working. A complete visual check of the vehicle’s wiring and the fuse box is the first step in identifying and fixing an electrical issue.

If you’re not comfortable checking your car’s electrical system, take it to a mechanic so they can properly diagnose and repair the problem.

❗Corrupt Condenser 

The condenser is an important part of the air conditioning system as it helps to cool the refrigerant. If the condenser is damaged or corrupt, it will prevent the refrigerant from being cooled properly. It will cause hot air to be blown into the car instead of cool air.

If you think the condenser might be damaged, take your car to a mechanic so they can properly inspect and repair it.

❗Cooling Fan Problem 

The condenser includes two cooling fans that serve to cool the refrigerant as it travels through the lines. The AC system will not work properly if they are damaged or malfunctioning. The first step in troubleshooting a cooling fan issue is to check the fuse box for a blown a fuse. If the fuse is not the problem, the issue lies with the cooling fans themselves.

If you’re not comfortable working with your car’s electrical system, take it to a mechanic so they can properly diagnose and repair the problem.

❗Bad compressor 

The compressor is responsible for circulating the refrigerant through the AC system. If it is damaged, it will prevent the refrigerant from being circulated properly and cause hot air to be blown into the car. Extended periods of inactivity, such as long winters without the need for air conditioning, may cause compressor problems. In order to avoid this, many modern cars leave the condenser running all year by enabling this in a defrost mode.

If you think the compressor might be damaged, take your car to a mechanic so they can properly inspect and repair it.

❗Dirty Air Filter 

A cabin air filter is available on several types and models of vehicles. A clogged or dirty air filter will prevent cool air from entering the car. It is because the air filter is responsible for trapping dirt, dust, and other debris before it has a chance to enter the car’s ventilation system.

Other signs that the cabin air filter is clogged are stinky odors or excessively loud sounds while using the AC. Like your home’s HVAC filter, your car’s air filter progressively becomes clogged with dust and debris, requiring regular replacement.

❗Stuck Blend-Air Door 

The blend door (also known as the “air mix door”) prevents warm air from flowing over the engines and into the vehicle when starting the car. If the blend door is stuck, it will cause hot air to be blown into the car.

No amount of cold air will ever go through a blocked blend door; you’ll only become hot and heated. The best way to fix a stuck blend door is to take your car to the mechanic.

❗Bad Compressor Clutch 

If the compressor clutch is not engaging, then the compressor will not be able to circulate the refrigerant. It will cause hot air to be blown into the car instead of cool air. The compressor clutch can become damaged due to various reasons, such as extended periods of inactivity or a faulty electrical system.

❗Faulty Expansion Valve

The expansion valve is responsible for regulating the flow of refrigerant. If it is damaged, it will cause the refrigerant to either flow too slowly or too quickly. It will prevent the refrigerant from being cooled properly, causing hot air to be blown into the car.

Cars are intricate machines with many different systems working together to keep you cool in the summer heat. If you’re having trouble with your car’s air conditioning, there are some potential causes. By troubleshooting the problem and ruling out each potential cause, you’ll be able to fix the issue and enjoy cool air all summer long.

Troubleshooting an AC Blowing Hot Air Problem

Before calling a professional, there are things you can check or minor troubleshooting steps you can take to try to fix the issue yourself.

✔Check the Fuses 

Start by checking the fuses. A blown fuse is one of the most common reasons why your AC is blowing hot air. The first step is to locate the fuse box and check for a blown fuse. If you find a blown fuse, replace it with a new one and see if that fixes the problem.

✔Check the Cooling Fans 

If the cooling fans are not working, they will not be able to cool the engine properly. It will cause hot air to be blown into the car. To check if the cooling fans are working, turn on the AC and wait a few minutes. Then, open the hood and see if the fans are running. If they are not, the problem is most likely with the cooling fan relay or the cooling fan motor.

✔Check the Thermostat 

If the thermostat is not working properly, it will prevent the coolant from flowing properly and cause hot air to be blown into the car. Start the car and let it idle for a few minutes to check if the thermostat is working. Then, feel the radiator hoses. If one is hot and cold, the thermostat is most likely working. If both hoses are cold, the thermostat may be stuck closed.

✔Check the Refrigerant Level 

If the refrigerant level is low, it will prevent the AC from blowing cold air. To check the refrigerant level, you’ll need a pressure gauge. Attach the pressure gauge to the low-pressure port and turn on the AC. The reading on the pressure gauge will tell you if the refrigerant level is low. If it is, you’ll need to add more refrigerant.

If you’ve checked all of these things and still have trouble with your AC, it’s time to call a professional.

Taking Care of Your Car AC to Last Long

Taking Care of Your Car AC to Last Long

A long ride on a hot day can be torture if your car’s AC isn’t working properly. So to prevent any issues with your car’s AC, here are a few things you can do:

Clean AC Deeply Annually or Periodically

There are two opinions whenever it comes to car air conditioner upkeep. The first requires having your car’s air conditioning system cleaned every year to minimize dust accumulation. In contrast, the second involves cleaning the internal components of the air conditioning system every several months.

If you are hesitant about whether to clean it every few months or every year, review your car’s warranty manual. Some late-90s vehicles, for example, need routine car maintenance, so if your car has an air-conditioning cleaning schedule, be sure to stick to it. You’ll be able to prevent expensive compressor repairs due to long-term negligence.

Use the Recirculation Feature

The recirculation feature on your car’s AC blows air that is already inside the car instead of pulling in hot, humid air from outside. This function is essential because it helps dehumidify the cabin quickly. Turn on the recirculation mode and leave it on for at least 15 minutes when you first start the car. Doing this will help cool the car faster and make the AC work less.

Don’t Forget About Your Car’s Sunscreen

Your car needs sunscreen, or it will get too hot inside, and your AC will have to work overtime to compensate. In other words, using sunscreen can save you money on gas. Sunscreens are easy to find and relatively inexpensive, so there’s no excuse not to use one.

Car's Sunscreen from Amazon

Use Car Aircon Properly

Once a week, for around 10 minutes, run your car’s air conditioner. It can keep the compressor running properly by maintaining gas pressure. Make sure it’s on the maximum fan speed and the coolest settings once you do it. Doing this will also help remove bad smells from your car’s AC.

Make Use of AC During the Winter

One of the key duties of ac is to make the car warm and eliminate moisture from the interior. It’s particularly useful for removing mist from the windshield to increase visibility. Thus, using your car’s AC during the winter will help remove moisture from the air, preventing the windows from steaming up. It will also help defog the windshield quickly.

Remove Dust from Vents To Avoid Corrosion, 

In order to prevent corrosion, you should clean the vents and passenger compartment air filter at least once a month. Dust that enters the system can cause blockages and lead to compressor failure. Use a brush attachment on your vacuum cleaner to remove dirt from the vents, then take out the passenger compartment air filter and gently tap it to remove any debris.

Replace Old Parts

Over time, parts of your car’s AC will break down and need to be replaced. The most common issue is with the compressor, which needs to be replaced every five years. Replacing old parts as soon as they break down will help prevent more expensive repairs.

Defrost for 5 Minutes Before Turning on AC

If you’re using your car’s AC in the summer, you should defrost the evaporator coils for five minutes before turning it on. It will help prevent ice build-up, which can reduce the system’s efficiency.

Get an Air Conditioning Service

One great way to keep your car’s AC in good condition is to get an air conditioning service. It will help identify any potential problems and prevent them from getting worse. It’s a good idea to do this at least once a year, or more if you use your car’s AC frequently.

Frequently Asked Questions

Q: How can I tell if my car’s air conditioner is low on refrigerant?

When the air conditioning system is low on refrigerant, you may experience some of the following symptoms:

  • The car takes a long time to cool down.
  • The air conditioning system blows hot air.
  • You hear a clicking noise when the air conditioner is turned on.

If you’re not sure whether your car’s air conditioner needs more refrigerant, you can take it to a mechanic for a diagnostic check. If it turns out that your car’s air conditioner does need more refrigerant, the mechanic can add more to your car’s system.

Q: How can I tell if my car’s AC compressor is faulty?

There are a few ways to tell if your car’s AC compressor is faulty. One way is to listen for strange noises when you turn on the AC. If you hear hissing, grinding, or clicking noises, there may be something wrong with the compressor. Another way to tell if the compressor fails is by feeling the compressor itself. If it feels hot to the touch, it may be overheating and need to be replaced.

Lastly, you can also check the air output of the AC unit. If there is little or no air coming out, that could be a sign that the compressor isn’t working properly. If you notice any of these signs, then it’s best to take your car to a mechanic and have them diagnose the problem.

Q: How often should I clean my car’s AC system?

It is best to have your car’s AC system serviced and cleaned annually. Dust, pollen, and other debris build-ups can clog your AC system’s air filters and ducts, impacting its performance and increasing fuel consumption. Cleaning the AC system also helps to improve the quality of the air you breathe inside your car.

Q: How long does a car’s air conditioner last?

How long a car’s air conditioner lasts depends on several factors, including how often it is used, the geographical location, and whether the car is regularly serviced. However, most car air conditioners should last around 5-7 years. 

There are a few things you can do to help prolong the life of your car’s air conditioner. Firstly, make sure that you have the system regularly serviced – at least once a year. It will help to ensure that any potential problems are spotted early and rectified before they cause any serious damage.

Secondly, suppose you live in an area with particularly hot summers or cold winters. In that case, it’s worth investing in an air conditioner cover – this will help protect the system from extreme temperatures and prolong its life. Lastly, try to use your air conditioner sparingly – if you can, open the windows and let fresh air in instead.

Q: How much does it cost to replace a car AC compressor?

The cost of replacing a car AC compressor can vary depending on the make and model of your vehicle. For instance, a Toyota Corolla will likely have a lower cost replacement than a Porsche 911. That being said, you can typically expect to pay between $400 and $1200 for the parts and labor needed to replace your car’s AC compressor. However, there are some tips you can follow to help keep costs down. 

First, check with your local auto parts store for any specials or discounts they may be offering on replacement compressors. You may also want to look online for coupons or promo codes that can be used at major repair chains. 

Final Thoughts

A well-functioning air conditioner is a must-have in any car – especially during the hot summer months. If you’ve noticed that your AC isn’t blowing as cold as it used to, read and follow the tips above to troubleshoot the problem. Don’t hesitate to take your car to a mechanic for a professional diagnosis and repair if all else fails.

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