Mold And Odour In Car AC Vents: How To Clean And Prevent

It’s a warm summer’s day and you need to run some errands, you start your car and turn on your ac to get the car to the temperature you like.

You’re then hit with a wall of stench that smells like sour milk and an old basement combined. Unfortunately, you’ve almost certainly got mold in your car ac vents.

Don’t worry, in this article, we will cover why you have mold in your car ac in the first place, how to get rid of it effectively and how to prevent it from coming back, all whilst adding in additional info that will help you win the fight.

So, if you want a fresh-smelling car that you’re not embarrassed to give people rides in, keep reading!

mold in car air conditioning vents

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Why does mold grow in your car ac?

Mold can grow anywhere that provides the correct environment for it to survive. All that mold needs are the following:

A moist environment (above 55% humidity)

A food source (this can be anything organic, such as skin cells, etc)

A dark environment (sunlight prevents mold growth)

As long as these needs are met, mold will thrive. This is why you often see it growing in places like basements and in high-humidity areas of a property.

Your car ac unit has all these resources. Moisture is provided by the condensate caused by the mixing of air temperatures, food is provided from dead skin cells, and the vents themselves stay mostly out of sunlight keeping them protected from the sun’s UV rays.

What are the signs and symptoms of mold in your car air conditioning vents?

Mold can be tricky, it can grow in the most tucked away and obscure place. That’s why it isn’t always easy to spot straight away. Here are some of the ways you might be able to tell if you are dealing with a mold problem in your car ac vents.


As I described in the intro, smell will be your primary symptom of an infestation of mold.

You might not always be able to see mold if it’s growing deep within the ventilation system of your car.

You should be on the lookout for a smell that only appears once you run air through the vents and that goes away once you turn the ac off.

The smell of mold has been described in many ways, but some people say it can smell like soured milk, whereas I think it’s best described as the same kind of musty smell you often find in old basements.

Breathing difficulties

If you have asthma or any other lung-related issue, you may find that mold spores can aggravate this and increase your symptoms. Breathlessness, a hoarse throat, and a runny nose are common symptoms of your body reacting to mold spores.

If you find that these symptoms only appear when you are sitting in your car with the ac on and quickly disappear when you leave the vehicle, you may well be dealing with a mold problem in your ac.

You MIGHT see it

As previously stated, the mold issue in the car ac may be difficult to spot initially, as they could be hidden deep within the system and out of sight. However, it is not uncommon for mold to form and grow around the supply vents, as this is where condensation can form, which provides mold with the moisture it needs.

The telltale signs of mold growth on an ac vent will be small, circular patches around the vent louvers and in close proximity to the vent opening.

The mold can come in various colors and textures depending on the type that’s taken up residence in your vehicle. Colors can include, blueish, grey, white, green, orange, or black. In terms of textures, the mold could be, fluffy, velvety, or even powdery.

How to get mold out of your car ac vents

Because mold spores can be hazardous to your health, it’s important to remove them as soon as it is first spotted.

Here are some effective methods of removing mold from your car ac vents.

Clean the filters

Your car ac unit will have filters that should be cleaned and replaced on a regular basis.

They are there to prevent debris such as pollen and mold spores from being sucked in and passed through your vehicle.

Often, these filters will become full of organic matter, which when combined with the appropriate level of moisture and lack of light, create the perfect environment for mold to thrive.

Make sure you are cleaning your filters on a regular basis using a HEPA- filtered vacuum and warm water/detergent solution. Only place them back once they are fully dry to prevent a further outbreak.

Supply vents

If you have noticed mold growth around the opening of the ac vent, you should begin to clean it by using a HEPA-filtered vacuum to remove most of the visible mold.

You want to do this before you begin wiping it in any way, as the vacuum will suck up any mold spores that are released, meaning you won’t find yourself with multiple new mold patches beginning to grow around the interior of the vehicle.

After using the vacuum, dip a cloth or sponge in undiluted white vinegar and gently wipe away any remaining visible mold. For the harder-to-reach areas (such as between the slats in the vent cover), you can use a thin paintbrush in the same way as the cloth.

Spray disinfectant through your vents

Making sure the engine is turned off, spray a disinfectant spray (such as Lysol), into the vents. Make sure you have found every vent in your vehicle to ensure you disinfect the entire air conditioning system.

Once you have sprayed all the vents, leave the car for a few minutes and then turn the air conditioning to its maximum setting and start your engine. Allow 10-15 minutes for your ac system to move the spray to all areas of the system.

Check the Ac unit drain tube

A commonly missed reason for mold growth in a car ac is a malfunctioning drain tube. If the tube becomes blocked with debris, for example, there is an increased chance that water could overflow onto the condensate pan, which gives mold a prime position to grow and multiply.

To clean your drain pipe, turn off your engine and find your drain line. This is usually a PVC pipe near the ac unit. Disconnect the hose and use a wire brush (pipe cleaner) to remove any blockages or debris.

Condensate drainage tubes can sometimes be tricky to locate, so if you cannot find it, or do not feel confident, you may prefer to ask a professional to clean it for you.

How to prevent mold growth in your car air conditioner

Luckily, there are several options available to you to prevent mold from occurring, and if you have had to deal with it in the past, these should prevent you from having to go through the remediation processes again.

Here is a list of the most effective ways of preventing mold and mildew growth in your car ac vents.

Keep your car dry

Even though your ac unit will create some moisture from condensation, keeping your car dry generally will help to prevent mold formation anywhere in the vehicle.

Cleaning up spilled drinks and drying out the carpets if wet shoes or umbrellas have been on them is a must if you want to stop the humidity levels from reaching the requirements of mold.

Disinfect the vents

Every few months you should spray a disinfectant through your vents. This will not only keep your vents smelling fresh but will also kill any mold spores that have settled in them and begun to grow.

Run the system

Mold hates to be disturbed, that’s why it prefers areas with a lack of airflow. Of course, your unit provides a great deal of airflow, but only if it’s being used.

If your car is in storage or you don’t have any plans to use it for several weeks, it is worthwhile running your ac at full power for around ten minutes or so.

You can also try shutting the ac off whilst the car is running for 5-10 minutes and then blasting the fan at maximum for several more minutes. This will help clear out any debris within the vents and also help to dry the system internally.

This will be long enough to blast out any mold spores that we’re trying to establish a colony in your vents. Of course, you should be wearing the appropriate safety equipment whilst doing this to prevent contact with the spores that are released.

Clean the filters

As we described earlier, your ac filters are the perfect location for mold spores to collect and reproduce, so make sure you are cleaning them using the steps outlined above and making sure they are completely dry before returning them.

Use baking soda or activated charcoal

Baking soda and activated charcoal work in much the same manner when it comes to absorbing excess moisture within a car.

They are hygroscopic, which means they are able to absorb water molecules from their surroundings. This helps by keeping your car’s humidity levels below 55%, which is what mold needs to live.

Simply open a box or tub of baking powder and leave it somewhere in your car, or add a few handfuls of activated charcoal to an open jar or tray and do the same. The moisture levels should begin to decrease within a number of days.

Is mold in your car ac vents harmful?

Many strains of mold can be harmful to human health, including those found within car ac vents.

Spores produced by green, red, white, orange, and black molds can cause breathing problems and nausea in some, whereas for others they can cause asthma attacks and serious allergic reactions.

For these reasons, even a small patch of mold should be removed as soon as it is noticed, as it can spread quickly. A car’s air conditioning will spread mold spores even faster, as it will blow the spores all over the vehicle, so it needs to be dealt with asap.

What kills mold in car ac vents?

To kill mold in a car ac vent, you have several options available to you. The best options are:

  • Undiluted white vinegar
  • Antibacterial sprays (such as Lysol)
  • Specific mold-killing products

When using chemical products to kill mold in a confined space such as a car, it is imperative that you open all doors and windows to allow as much airflow as possible.

You should also not use hydrogen peroxide or bleach products to clean your car ac units, as not only can they damage and stain the interior of your car (and the ac system), but they also produce toxic fumes that should not be inhaled. There are plenty of natural products and specifically designed products to do the job.

How to get the musty smell out of your car ac vents

One of the main symptoms I described of mold growing within your car ac vents is the terrible smell it produces.

Unfortunately, even if you do manage to remove all the mold from the vents, the smell can linger for several days. Fortunately, there are several highly effective methods to remove the musty smell that comes from mold and mildew infestation.

Air it out

One very simple method is to open all the doors and windows to allow the car to receive as much airflow as possible. Within only a few hours, you should notice the smell has begun to dissipate.

One word of warning only use this method in dry conditions. If you introduce moisture back into the vehicle, you’re likely to have to deal with the problem all over again.

Use baking powder

Baking powder is an excellent way to absorb excess moisture, and it is also great at absorbing unwanted smells.

To use it to remove the smell of mold, leave an open box of baking powder on the floor of your car or the boot. Within 24 hours you will notice the smell beginning to improve. Just remember to take it out before you drive your car again.

Activated charcoal method

Activated charcoal works in much the same way as baking powder, in that it is excellent at absorbing moisture and odors.

In a jar or on a tray, place several handfuls of activated charcoal. Leave the jar or tray on either the seats or in the boot. And within a few days, you will notice the smell being to become less powerful.


Finding mold in your air conditioning unit is a frustrating experience, but it can also be a health hazard, so it’s important to get it resolved as quickly as possible.

Make sure to keep your car as dry as possible, run your ac on full power once or so a month for a few minutes, and keep your car clean and you should have far fewer problems with mold to deal with.

Chris Walker

Chris Walker has struggled for several years with mold after buying his own property. After finding the solutions to several issues around his home, he decided to create this site in order to answer as many questions about mold and mildew as possible to help others dealing with the same problems.

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