Why Does My Air Conditioner Smell Musty?

There’s nothing better than escaping the scorching heat of summer and relaxing in your air-conditioned home. But when you catch a whiff of a strange, musty smell, you need to act fast. Why does a musty smell coming from your air conditioner mean?

In short, a musty smell indicates bacterial growth build-up, which forms on the drain, evaporator coil, or in the drip pan or drain line of your AC. Your evaporator coil is a dark and humid location, so all sorts of mold and mildew can grow, which causes that unpleasant, musty smell. We will cover the steps you need to take to find the source of the musty AC smell and how to fix it, including:

  • Check if your AC drain pan is full
  • Check for frozen evaporator coils
  • See if there is excess moisture in your ducts or vents
  • Identify if there is a blockage in your condensate line
  • Determine if your AC unit is not the right size for your home

Because the air coming from your AC vents isn’t supposed to have a smell, you’ll need an expert HVAC company if you notice the equipment letting off a musty odor a little while after adjusting the thermostat to a cooler setting.

Let’s take a look at why you need to act fast when you notice a strange smell and five common reasons why your air conditioning unit smells funky.

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Why Are Strange Smells An Issue?

Whether you notice the smell of dirty socks, rotten eggs, or mildew permeating from your ductwork, all smells indicate an underlying issue with your AC unit.

Sometimes your HVAC unit may emit a burning smell at the start of the cooling or heating season as dust that has settled in your unit burns off. If you smell rotten eggs could mean you have a gas leak or a dead animal in your vents. A dirty sock smell, or musty smell, means you could have a mold issue.

A musty odor typically means there could be contaminants present in your air conditioning system. Because your system is a dark and humid place, it’s a breeding ground for bacterial growth.

This means that your AC is spreading dangerous mold spores into every room of your home. These spores can cause severe health issues, especially if one of your family members struggles with allergies.

Homeowners should never ignore strange smells coming from their HVAC systems. The best way to get to the bottom of your odor issues is to call a professional air conditioning technician to evaluate your system.

Five Reasons Why Your AC Smells Musty

As you wait for your air conditioner technician to arrive, it’s helpful to troubleshoot to guide them to where the potential issue is occurring. This will speed up the process and ensure your HVAC unit gets repaired the first time correctly and your home smells fresh once more.

Here are five common reasons why your AC has a musty smell and where you can look to determine if that is the problem.

1. The Drain Pan is Full

Because your AC unit removes humid air from your home, it causes water droplets to fall into the drip or drain pan. This part of your HVAC system endures normal wear and tear, which means its functionality will deteriorate over time.

An ineffective drip pan will accumulate mold, which causes the smell in our home when the unit is running. Your local HVAC technician can replace it with a new one to remove the odor.

Where To Look: The drip pan is located directly underneath your system’s evaporator coils. 

2. Frozen Evaporator Coils

Your air conditioner absorbs warm indoor air, removes the humidity while cooling it, and cycles the air back through return vents. Unobstructed airflow is essential for this process, so air filters must be clean.

Dirt and debris will block airflow, which causes water droplets from the humid indoor air to build upon the evaporator coils. These water drops will freeze as the AC unit’s refrigerant cools the air. Your HVAC technician will need to let the condenser coil thaw and change the filters to restore maximum airflow.

Where To Look: The evaporator coils are located inside or near the air handler, where the blower fan is in your unit.

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3. Excess Moisture In Ducts Or Vents

When excess moisture accumulates inside air ducts and vents, it’s caused by high humidity levels or a drainage leak. If you smell something musty as soon as you turn on the AC unit, there’s a chance that mold and mildew have made their way into your ductwork.

Mold exposure can cause upper respiratory health issues, so call a professional HVAC technician as soon as possible. Your ducts and vents will need to perform duct cleaning and repairs to remove the musty odors for good.

Where To Look: Your ducts are attached to the vents in your home. Some ductwork may be in the ceiling or in a crawlspace, which means a professional will need to access it to ensure the mold issue isn’t extensive.

4. Blocked Condensate Line

The unit’s condensate line is a small pipe, typically made of PVC, located next to the condenser unit. The condenser unit is the part of your air conditioning unit located outside of your home. Its job is to drain water from the drip pan into your landscaping or storm drain.

It’s also one of the top locations for mold, mildew, and sludge to build up because of its small size. This leads to clogs, and of course, musty odors in your home.

To Look: The condensate drain line is a small pipe that runs from your home interior to the outdoor portion of your unit.

5. Incorrect AC Size For Home

For your AC system to work correctly, it needs to be the correct size for your home. If it’s too large, the air gets cycled too quickly, leading to a lack of dehumidification and an increase in excess moisture. If it’s too small, it will turn on and off constantly, leading to premature failure.

Ask your HVAC technician to check if your air conditioning unit is the correct size. HVAC unit sizing is about more than your home’s square footage. Your service technician will also consider the number of people who live there, your home’s insulation type, and your needs based on your local climate.

Where To Look: Ask your service technician to evaluate your system.

Trust R & T Services To Solve Your Air Conditioning Odor Issues

When your cooling system emits a funny odor, call a professional right away to prevent harmful contaminants from compromising the air quality of your home.

Don’t forget to schedule routine air conditioning maintenance to prevent musty smells from developing in your home.

The air conditioning technicians at R&T Services have been troubling shooting air conditioning issues in Billings for over 30 years. We take pride in our professional knowledge and extensive professional knowledge.

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We are the first choice for Billings AC repair services. Talk to our AC experts today!

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