Informational Guide

Window Air Conditioner Smells Musty?

Learn how to easily get rid of common and annoying musty smells in your window air conditioner.

by Josh M

We love living in comfort, and air conditioners help lower the temperatures indoors so that you can sleep, work, and exercise comfortably indoors. However, water, heat, and dust in an AC can lead to the dirty sock syndrome, where the unit produces a foul smell.

Luckily, there is a way to get rid of this syndrome quickly. If your window air conditioner smells musty, follow this guide to get things back in order.

Window AC With Cream Curtains
Mold & Mildew Growth

Mold and mildew are found almost everywhere and can grow on any surface, provided oxygen and moisture are available.

Water does collect at the bottom of the air conditioner, and combined with the constant airflow, expect mold and mildew to grow naturally over time. The two produce a musty scent that resembles the smell of wet socks or rotting wood.

Dirty Or Damaged Evaporator Coils

Evaporator coils collect dust and dirt over time and are perfect breeding grounds for mold and mildew because they get warm and moist. These factors can lead to horrid smells while also blocking some air from flowing past the fins.

Clogged Drain Line

Water from the evaporator coils collects in the condensate pan and gets flushed away via the drain line. Sometimes dust can clog the drain line, leading to an accumulation of water inside, which accelerates the growth of mold and mildew.

How To Get Rid Of Musty Smells In Your Window AC (Easy Steps)

Since the root of the problem is the growth of mold and mildew inside the window AC, the only way to eliminate musty smells is to clean the components inside.

You will need a screwdriver, spray bottle, dry lint brush, a blower, a hose, damp cloth, and rags.

Step 1: Unmount The Window AC

Place rags under the unit before unmounting to absorb any water that pours out from the condensate pan. Next, unplug the AC and remove the front cover by unfastening the screws holding it in place using the screwdriver.

Remove the insulation around the window, then unfasten the AC from its mounting base and pull it out.

Step 2: Take It Outside

Take the unit outside and place it where you can hose it. You can put it on a firm table on your driveway.

Step 3: Blow Off The Dust

Begin cleaning by blowing off the dust using a blower. After this, wipe any dusty surface using a damp cloth. Be gentle, especially on the dust fins, because they are soft and can bend easily.

Step 4: Clean The Fins, Vent, And Blower

Clean the spaces between the fins using a soft lint brush. Stroke them gently up and down to brush off the dirt caked there over time.

Next, clean the vent and blower by spraying a solution of bleach and water. Flush with plain water afterward to get rid of the bleach.

Step 5: Clean The Condensate Pan

Using a hose, pour water over the condensate pan to flush out the mold and mildew, which will be mucky. Do not spray. Pressurized water can damage the components.

Step 6: Leave It To Dry

Wipe any other dirty surface, then leave the AC to dry outside for a few hours.

Step 7: Reassemble And Mount Back To The Window

Reassemble the unit and mount it back to the window.

Window AC on a Black Framed Window

Other Unusual Smells Found In Air Conditioners

Window AC smells differ, and these usually signal other issues, not mold and mildew. You might get these smells:

Burning Smell

A burning smell usually results from dust settling on the condenser coils after long periods of inactivity. When you turn on the AC, the dust burns, and it should go away after some time.

However, if the smell persists, it could be due to burning electrical parts or overheating components. The solution is to turn off the AC and get a professional HVAC technician to look at it.

Rotten Eggs

If you smell any rotting odors, it is due to rodents or small animals that have died somewhere inside the unit. Remove the front cover to access the interior, then remove the animal.

Skunk Spray

Air conditioners circulate air in your house, and if there is a gas leak, you will smell what resembles skunk spray. Since natural gas has no scent, utility companies add Methyl Mercaptan to give an odor that ensures easy detection in case of leaks. The solution is to shut off the gas supply and call your utility company to fix the issue.

Cigarette Smoke

Evaporator coils and filters tend to absorb odor from the air passing through, so if you smoke in the house, this scent will stick to these components eventually.

When you turn on the AC, the stuck smoke particles go back to circulation, causing the smell. Changing the filter and cleaning the unit will solve this problem.

Exhaust Smell In Car AC

If the window air conditioner smells like chemicals or has an exhaust-like smell, the cause is leaking refrigerant. Such gases are harmful to you and the environment, so you should have a professional check your unit as soon as possible. Meanwhile, keep the windows open to ventilate your home.

How To Prevent Your Window AC From Smelling Bad

The only way to keep your AC from producing foul smells is to clean it regularly, including the filter. You can replace the filter instead of cleaning it if you choose. Not only is this good for improving the air quality, but it makes the unit more energy efficient.

When dust, mold, and mildew clog the evaporator coils, they reduce the surface area for heat exchanging. As a result, the unit will have to run for long periods to lower the temperature, which results in higher power bills.

Washing AC Filter with Water

People Also Ask (FAQ)

What does a Freon leak smell like

Leaking freon smells like sweet chloroform or a sweet-smelling version of car coolant. Some describe the smell as similar to nail polish remover, which contains acetone.

Why does my AC smell like acetone?

The most probable cause is a refrigerant gas leak. There is no standardized AC fluid for all units, so manufacturers can use different refrigerants. These produce unique smells when they leak, and in most cases, an acetone smell is leaking freon.

Can I spray bleach in my window air conditioner?

You can only clean the vent and fan by spraying a solution of bleach and water. For the other parts, either use water, a damp cloth, or a dry lint brush.

Can you spray Lysol in the window air conditioner?

No. You can only use Lysol to clean the coils at the back of the unit with a stiff brush and wash the air filter. Do not spray the other parts.

Conclusion

As you can see, your unit can produce different smells, each signaling a particular issue. However, if the window ac smells musty, it means mold and mildew are growing inside. The solution is to clean the interior, and the steps above will help you get the job done.

Josh M

My name is Josh and I am obsessed with the HVAC industry. I created this website to help HVAC techs of all levels get the best out of their heating & cooling systems. I have spent thousands of hours studying air conditioners, heaters and home air products so you can learn & buy with confidence. Learn more about the team here.

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