Why Your Car AC Smells Bad & Solutions


Have you ever turned on your car AC and noticed an unpleasant smell shortly afterward? This is frustrating when you want to go for a pleasant drive on a hot day – but how can you combat it? Let’s find out!

There are a few potential causes for a bad smell, including mold building up in the evaporator core, or unpleasant odors in the cabin of the car being sucked into the filter and accumulating over time. Alternatively, the AC evaporator may be leaking refrigerant, which will produce a chemical smell.

In this article, we’ll explore the potential causes of unpleasant odors in your AC, and look at what you can do to solve them!

Mold Buildup

Sometimes, water condensation will collect inside the housing of the AC. This is because the AC coil is cold, and hot air gets blown over it – meaning that moisture droplets that have evaporated into the air condense and form as water on the coil.

Most visible place for mold are the air vents, although, most of the time it will be somewhere completely invisible

In theory, this moisture is carried out of the car using a drain line, but sometimes, pockets of moisture remain and do not get carried away from the coil.

Over time, this water will start to breed mold and fungus, especially if you live in a hot climate that keeps your car warm and provides the mold with good breeding conditions.

When you turn the AC on, the air will then blow around, spreading the tiny particles throughout the car, where you breathe them in. This creates a musty, unpleasant smell, and could be dangerous to your health.

The Solution

Because the mold will be inside your system, you may need to get it cleaned out at a garage. However, you might be able to dry it out yourself if the problem hasn’t got too bad yet. The first thing you should do is run the AC on full for a while, and then turn off the AC but keep the fan running.

The fan will ensure that air keeps circulating through the system even once the evaporator coil is warm, and this will help to dry the water out and stop it from sitting on the core. Without water, the mold will dry up and die, and the smell should go away.

It is often a good idea to let your car’s fan run for about 5 minutes after you have turned the AC off, so try to get into the habit of doing this whenever you drive somewhere. This will help to ensure that the evaporator coil always dries out, and will minimize the risk of mold building up in there.

Bad Smells In The Cabin

If you’ve got unpleasant smells in the car on a regular basis (even things like food can cause bad smells after a while), you may find that the AC starts to smell horrible. Cigarette smoke, wet clothing, pets, etc., can all cause this issue. The AC will suck in the smells when it’s operating, but the particles won’t necessarily be released.

These particles will sit in the AC unit, building up and moldering, and when they do blow back into the car, they will create a musty, unpleasant odor. Cigarette smoke is a particularly big offender, so be aware of this if you smoke or if you are buying a used car.

All of these particles will start to clog up the cabin’s air filter, which will stop it from functioning properly, as well as causing an unpleasant scent. If the air filter isn’t working, other AC components will get stressed and may burn out. It is therefore important to address this.

The Solution

You should regularly get the air filter in your cabin replaced. Ask your local garage to do this, or learn how to do it yourself, and make it part of your car’s maintenance routine. Keeping this filter clean and fresh should ensure that the AC doesn’t make the inside of your car stink.

You should also minimize the smelly things that you carry in your car when you have the AC on. This may not always be possible, but opening the windows or letting things air out before you put them in the car can help. 

If you can’t avoid carrying something smelly, make an effort to air the car out when you reach your destination, rather than shutting the smell in the cabin.

This video also showcases a method with lysol

Refrigerant Leakage

If you notice a chemical-based bad aroma, there is a high chance that the refrigerant in your AC is leaking out of the AC evaporator. This refrigerant will make a strong, unpleasant smell, and it will also stop your AC from working properly.

The refrigerant contains oil, and this will trap dust on the evaporator fins, which will gradually build up and start to restrict the air flowing through the system. If you put your hand in front of one of the vents, you might notice that there is only a small amount of air movement, even when the AC is on full.

Again, this will put pressure on the system and should be fixed as soon as possible.

The Solution

Because this problem is inside the AC unit itself, you will need to get a repair done at the garage. You risk damaging your car if you attempt to repair or replace it at home, so let professionals do this job for you.

How Does a Car AC Work?

An air conditioner is considered an essential in cars these days, and it works to pull both heat and humidity out of the air in your car. It then cools the air down and blows it back into the cabin. It outputs the heat and the humidity into the outside world.

Air conditioners work by using a refrigerant, which is a special chemical that helps to cool the air. They have three major components: a condenser coil, a compressor, and an evaporator coil. 

When the AC is operating, it converts the refrigerant from a gas into a liquid, and then converts it back into a gas again. 

The refrigerant starts in the compressor, which converts it into a gas form, and then sends it into the condenser coil. In the condenser coil, it is converted back into a liquid, and then it is drawn back into the indoor space and into the evaporator coil.

The liquid then evaporates within the coil. The refrigerant absorbs the heat and makes the coil cold. A fan is constantly blowing air from inside the car across the evaporator coil, and the cold coil makes the air cold too.

The fan blows this cold air into the car, circulating it through the cabin, and the hot refrigerant gas is returned to the compressor. The heat is released into the air outside the car, the refrigerant gas turns back into a liquid, and the process is ready to start again.


A few different things can cause a bad scent in your AC, and it’s a good idea to address them as quickly as possible. Not only is the smell unpleasant to deal with, but it may cause health issues if it contains mold spores, or it could indicate that your AC system is being put under pressure by particle buildups or leaked refrigerant. Take swift action if you can!

Leave a Comment