Why Does My Car AC Smell Musty?

Musty smell from car AC

Have you ever started up the air conditioning in your car, only to be knocked over by a musty smell that is reminiscent of old gym clothes?

This problem isn’t unusual, especially with all that can go wrong with the car’s AC system. Thankfully, you don’t need to deal with this musty smell from the car AC for long if you know how to fix it.

The proper way to resolve the problem is first to figure out what’s causing the smell. We review some of the top problems you might encounter. After that list, you’ll find the best fixes, ensuring you can breathe easy once again. At the end of this guide, you’ll also find a few answers to questions that have been asked recently. 

Causes Of Musty Smell From Car AC

Unless you’ve actually left dirty clothing or rotting food in the car, your smell is coming from something more serious. It could be as simple as a dirty cabin air filter or a dead animal. It’s also possible that you are dealing with excessive condensation or mold in the vents or on the evaporator coil.

Here is a more detailed list of what could cause a musty smell from your car’s AC:

1. Dirty Or Old Cabin Air Filter

dirty cabin air filter

The cabin air filter might not be talked about as much as the engine air filter, but it also has an important purpose. This air filter traps contaminants and dirt that would otherwise circulate through the cabin. Because the filter grabs all of the tiny particulates, your cabin remains a better place for your respiratory system, especially if you have asthma or other breathing problems.

However, if you miss the recommended schedule to change the air filter, it could become clogged. Because there is dirt sitting on the filter, the AC now circulates these harmful particles in the cabin, leaving you with trouble breathing and a musty smell. 

READ MORE: 5 Symptoms Of A Bad Cabin Air Filter (& Replacement Cost)

2. Mold In Vents

The car’s ventilation system contains a lot of ducts and hoses. Within this system, condensation begins to build up. As the air pushes through the system, its last stop is through the vents of the cabin. Here’s where a lot of the condensation rests.

Because most people don’t take the time to deep clean the car vents, mold can start to grow. Not only mold, but the vents can also spawn bacteria that can get you sick. If you notice a musty smell, take a look at those vents to see what’s growing. 

3. Moldy Evaporator Coil or Fins

The various parts of the air conditioning system are also susceptible to all of this condensation. Depending on the design of the system, water can get trapped on vital components, where cleaning never occurs.

Two parts that suffer from mold occasionally include the evaporator coil or fins. The evaporator is meant to remove heat and take out humidity. Additionally, the condenser fins can become damaged, allowing more moisture to remain trapped. Either way, mold starts to grow and you get a noxious smell in the cabin. 

4. Excessive Condensation

The car air conditioning system is designed to drain water from the vehicle. All of the condensation that builds up is supposed to circulate through to the drain under the car. That’s why you might see water leaking under the vehicle when the AC is on.

However, these drains are prone to getting clogged. When that happens, condensation builds up in the system and mold can grow. 

5. Dead Organic Material

dead mouse in car

Your car is an inviting place to critters everywhere, especially when the weather is cold. As animals look to find shelter from the elements, they may climb inside the systems of your vehicle. If you start the car without knowing they have taken up residency, the animal could die.

After a while, all dead animals start to smell. Eventually, you will start to get a whiff of the matter through your car AC vents. 

How To Get Rid Of Musty Smell From Car AC

If you want to remove musty smells from the car, you can quickly work through this list we’ve put together. Many of these tasks should be done regularly, while others only need to be performed when there’s a problem. 

1. Replace Cabin Air Filter

The majority of manufacturers recommend having the cabin air filter changed every 15,000 to 30,000 miles. To get the recommendation for your vehicle, look for the maintenance schedule in your owner’s manual. 

If you want to change the cabin air filter yourself, follow these simple steps However, the location of the cabin air filter depends on the car model. So check a repair manual or do research online for your car model.

Here is how you replace the cabin air filter in many car models:

  1. Open up the glove box. 
  2. Remove the limiting arm on the right side of the glove box.
  3. Release the glove box. This reveals the opening of the cabin air filter.
  4. Take out the old cabin air filter. You may want to wear clothes to avoid contact with all of the dirt and dust.
  5. Install the new cabin air filter.
  6. Replace everything in the opposite order.

On average, a new cabin air filter only costs between $20 and $65. For this cost, it doesn’t make sense to deal with stinky smells any longer. 

2. Clean Air Inlet and Drain From Leaves & Dust

leaves car inlet

At the bottom of the windshield, you’ll find air inlet holes that are used by the air conditioner. When leaves and debris clog these holes, condensation occurs. It’s simple to clean up the leaves and dust by wiping them off. They should also come off whenever you wash the car.

Additionally, you need to make sure the drain under the vehicle remains open. You may need to use compressed air or a metal wire to get clogs out of the drain pipe.

3. Use an Air Conditioning Cleaner

clean vents car

Search for a high-quality air conditioning cleaner to use in your car. It’s often best to pay a little more for a better cleaner. Read all of the directions before using it or follow these generic steps. 

  1. Dry out the air conditioner. Turn the temperature as high as it goes and set the fan to the maximum option. 
  2. Once the AC is dry, turn off the car engine.
  3. Remove the cabin air filter. 
  4. Spray the cleaner into the filter housing and the AC vents. 
  5. Allow the cleaner to sit for the specified time on the bottle.
  6. Turn on the car and run the AC for another five minutes. 

If the smells are really bad, your AC system may require multiple treatments. Check the bottle to see how often it can be used. 


4. Ozone Treatment

Many auto detailers rely on the use of gas ozone generators to remove odors and bacteria from the vehicle. A generator can be placed in the vehicle for a certain amount of time to neutralize the smells.

If you plan to do the ozone treatment yourself, consider these steps.

  1. Remove all loose items from the car.
  2. Vacuum the interior of the car.
  3. Don’t leave any kids or animals in the vehicle while performing the treatment.
  4. Put the ozone generator in the vehicle or attach the hose as indicated in the manual.
  5. Run the machine. You may need to run it between 30 and 120 minutes.
  6. Open all of the doors and allow the gases to dissipate. 
  7. Repeat the steps if there’s still an odor.
  8. Wait an hour before you enter the vehicle. 

Some people notice an ozone smell after the machine is done. This can take up to a week to go away completely. 

5. Clean Vehicle

Above all, it’s important to clean out the vehicle. If you are noticing any unpleasant smells, cleaning the car should be the first step you take. The way you clean the vehicle depends on what needs to be done, but here are a few steps to consider.

  1. Remove any loose items that don’t belong.
  2. Remove the floor mats and clean them.
  3. Vacuum the interior.
  4. Dust the dashboard.
  5. Clean the console, cupholders and all of the crevices.
  6. Wipe down the windows.
  7. Protect the seats with an appropriate cleaner. If you have leather seats, they should be conditioned.

Go ahead and add an air freshener to the car. You can use something natural, such as baking soda or charcoal, to keep odors at bay. 

How do you get rid of the funky smell in AC?

Start by cleaning out the car and the AC vents. You should also change the cabin air filter. If mold is building up in the air conditioning system, you may need to get professional help to deep clean. Also consider using an ozone generator to remove odors. 

Can the musty smell from AC make you sick?

The smell isn’t what’s going to make you sick, but the mold that causes the smell could. Any bacteria or mold that grows in the system can lead to health problems. These are most noticeable if you have respiratory illnesses, such as allergies or asthma. 

Why does my AC smell musty when I turn it on?

There’s probably a buildup of mold or mildew somewhere in the air conditioning system. When condensation can’t drain from the system, the excessive moisture leads to mold growth. When you turn on the blower, it causes a noxious smell that’s reminiscent of a locker room. 

How do I know if my AC has mold?

The musty smell is a tell-tale sign that mold is growing in the air conditioning system. You may also notice some of the mold in the vents, on the mechanical parts or in the cabin air filter. To remove the mold, you need to clean the car and the air conditioning system. 

There’s no reason to deal with a musty smell coming out of the air conditioning. Instead of dreading every drive in your car, you can enjoy the open road once again. Deal with the mold issue to get rid of the mold once and for all.

Of course, the best way to ensure you don’t have to deal with these musty smells is to prevent buildup from occurring in the first place. Keep your car clean and fix any mechanical issues as they arrive.

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Categories: Air condition, Cleaning & Detailing

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