AC Smells Musty

AC Smells Musty

AC smells mustyIf you start up your air conditioner and notice a musty odor similar to wet laundry that’s been left sitting, you’re most likely smelling mold or mildew. Unfortunately, this is a common problem with air conditioners.

Mold and mildew develop in places with high moisture content, so your air conditioner is a prime candidate. This fungus not only smells bad but is also capable of triggering allergies and worsening asthma symptoms.

To make matters worse, your AC is distributing the mold and mildew spores all throughout your home while it runs.

For these reasons, it’s important to discover the cause of the problem and take steps to remedy it.

4 Reasons Your AC Smells Musty

Here are some of the most common reasons your air conditioner smells musty and what you can do about it.

1. Clogged AC Drain Line

When you smell mildew in your AC unit, this is likely because mildew is actually growing inside of it. This often occurs when the unit’s drip pan accumulates water. The water becomes stagnant, which provides an ideal environment for fungal growth. The drip pan may fail to drain properly if the condensation drain line becomes obstructed or damaged.

Solution: Unclog your AC drain line and clean it regularly to prevent this problem in the future.

2. Mildew in Air Ducts & Vents

In areas with high humidity, it’s not uncommon for moisture levels in homes to become an issue. This allows mildew to form nearly anywhere, particularly in the vents and ducts running from your central air unit.

Solution: If the smell of mildew is wafting from your AC vents, it’s strongly recommended that you have them inspected. If it’s discovered that there is indeed mildew growth, you can get rid of the unwanted smell by having the ducts professionally cleaned.

3. Improperly Sized System

Mildew growth may also become an issue if your air conditioner is too large for the room or house it’s being used to cool. In these cases, the AC unit pulls in the fresh air too rapidly, which prevents it from being sufficiently dehumidified. Excessive humidity causes mildew to grow in not only the unit but also your walls, upholstery, carpet and other areas of your home.

Solution: If you suspect that an oversized AC unit is causing your mildew problem, you may wish to consider having it replaced with one that is a more appropriate size for your needs.

4. Dirty Evaporator Coil

When your evaporator coil is dirty, it can become a breeding ground for mold.

Solution: If you haven’t had maintenance performed on your AC system in a while, it’s probably time to call a local HVAC company. Many will clean the evaporator coil as part of a routine maintenance visit. Alternatively, you can install a UV lamp to prevent mold from growing on the coil.

3 Replies to “AC Smells Musty”

  1. I didn’t know that mold will begin to accumulate and produce a musty smell if your evaporator coils are not clean. My wife and I have been unable to sleep with our window air conditioner on because it emits a strong odor if we keep it turned on for more than an hour. We’ll consider hiring a professional to help us fix our unit.

  2. Thank you for explaining how your drip pan may not correctly drain if your unit’s condensation drain line has been damaged. My wife and I have noticed that our window air conditioner in our bedroom smells like mildew, and we are worried that it was damaged when we accidentally dropped the unit last week. Maybe we should consider hiring a professional that can help us fix our system.

  3. Thank you for talking about how mildew can form in ducts and vents and produce grassy smells when unattended. The other day, we were wondering why we were smelling something similar to a garden even while sitting in our living room far from the garden. We thought that this was because we recently installed decorative plants in our living room, but even after removing them, we still continued to experience the smell, so we’ll definitely get an HVAC contractor to look at our ducts and see what might be causing this smell.

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