We're Always Open Call Us Today!

Why Does My Air Conditioner Smell Like Mildew?

Why does my air conditioner smell like mildew?

It’s a good question.

When the days turn hotter and you walk into a stuffy home, you’ll probably immediately turn on your air conditioner.

However, there are times when you can experience the strong musty odor of mildew.

Initially, you may not even realize that the smell is coming from your air conditioner, as the smell can often resemble the stick of wet laundry left in the washing machine too long.

The only thing worse than a hot day is a hot day and a foul stench coming from your air vents.

It’s very important to address the problem quickly because mold and mildew can cause health issues.

So why does your AC smell of mildew?

1. Clogged or Dirty Filters

  • Mold can start to grow on your filters if exposed to water or if they become clogged or dirty

The filter traps organic particles which, when exposed to moisture, will encourage mold growth.

Check your filters – if they look clogged or overly dirty, replace them.

2. Clogged Drip Pan

  • A clogged drip pan will fill fast and leak

This can happen due to the pan being incorrectly positioned or an actual clog around the drain port on the air conditioner.

A simple clog is easy to remedy yourself, but, if the pan is incorrectly installed you are best off calling a professional.

3. Clogged Condensate Drain Line

  • If the condensate drain line is clogged, mildew can grow on and around the coil

Your condensate drain line goes from the coil drain pan to either a condensate pump or a nearby floor drain, and eliminates condensation produced by the coil.

4. High humidity and mold

  • High moisture levels in the duct work can cause mold and mildew, spreading the odor throughout your home

If there are high humidity levels within your house, then mold can grow virtually anywhere.

You will need a professional to inspect the ducts and vents, as trying to do this yourself can negatively impact your air conditioner’s efficiency.

You may also have a more complicated internal HVAC problem which will need to be diagnosed by an AC technician.


Today’s article provided some easy ways to troubleshoot mildew smells coming from your air conditioner.

However, you may have problems that require professional help.

Do you need more information? If you would like to talk about your air conditioner smelling like mildew, or a related topic, please contact us at (651) 294-7798.

We cover Blaine, Bloomington, Brooklyn Park, Eagan, Edina, Hastings, Maplewood, Minneapolis, Minnetonka, Roseville, North Saint Paul, Saint Paul, Saint Paul Park, South Saint Paul, Stillwater, West Lakeland, West Saint Paul, White Bear Lake, Woodbury, and many more locations.

Can’t find your town listed? Contact us at (651) 294-7798 to tell us where you live, so we can help you get rid of your AC mildew odors.

Schedule a HVAC repair anywhere in the Minneapolis or St. Paul area today by calling (651) 294-7798 or by requesting an estimate online.


Contact Us

1220 Cope Avenue East, Maplewood, MN 55109