Understanding why your AC smells musty and how to fix it

Why Your AC Smells Musty: 4 Causes — and What To Do About It

While a temporary musty smell from your AC after winter in Amarillo is normal, a persistent odor can hint at underlying issues. If your AC unit smells musty and circulates unpleasant odors throughout your home, it can be a sign that it’s harboring mold and mildew and sending spores and other allergens into your rooms.

Here are some of the possible reasons why your AC smells, what you can do to prevent it, and when to call in the HVAC experts at Frank’s.

4 Possible Reasons Why a Musty Smell is Coming from Your Air Conditioner

When your AC smells musty, a few factors may be to blame.

1. Your condensate drain pan is full

The condensate drain pan catches the humidity your AC removes from your home’s air and sends the excessive moisture through a drain tube that usually terminates outside your home. Drain pans can sometimes clog and fail to properly drain water, leading to mold growth if not properly maintained. If you notice an odor that smells like dirty socks, it might be time to clean, empty, or replace the drain pan.

Depending on the specific model and type, AC systems vary when it comes to how many drain pans they have, where they’re located, and how to remove them. During routine spring AC maintenance, your HVAC technician will inspect and clean the condensate pan.

2. Your condensate drain line is clogged

The condensate drain line is the pipe that routes water from the drain pan to outside your home. Condensate drain lines easily clog with bacteria, dirt, and other debris; combined with moisture, this becomes the ideal environment for mold growth.

You can clean your condensate drain line yourself between routine maintenance with just a few household supplies and the following steps:

  • Disconnect power: Shut off the AC’s power at both the thermostat and the breaker switch.
  • Locate access point: Locate the T-shaped pipe fitting attached to the indoor drain line. Remove the cap.
  • Unclog and flush: Remove any obvious and accessible blockages by hand. Pour distilled vinegar or another mild cleaning solution into the line. Flush the line with water to move any residual solution and debris, and return the cap to the fitting.

If a simple cleaning isn’t enough to clear the line, the pros at Frank’s unclog it in no time.

3. You have excess moisture in your ducts

While a small amount of moisture in your ducts is harmless, excessive moisture can lead to high indoor humidity — the ideal condition for mildew, mold, and musty odors. Condensation in ductwork is a common problem that can stem from various underlying issues, including mechanical malfunctions, improper AC size or installation, poor insulation, leaky or clogged ducts, or a dirty air filter.

In addition to a musty or moldy odor when your AC is running, signs of excessive moisture in your ducts include:

  • Visible mold or mildew on the duct surfaces
  • Water stains on the wall or ceilings around your air vents
  • Visible condensation on the exterior of your ductwork
  • A noticeable increase in indoor humidity levels

If you suspect excess moisture in your ducts is responsible for the musty smell, a few DIY fixes might help:

  • Regulate humidity levels with a dehumidifier — the ideal home humidity level is 30% to 50%.
  • Replace your air filter when it’s dirty — at least every three months. 
  • Add insulation to metal ductwork to help prevent condensation from building up.

If the problem persists, a professional duct cleaning may be in order.

4. Your air filter is dirty

Your AC unit’s air filter traps dust, bacteria, dander, and other particles that can pollute your home. Without proper maintenance, air filters can clog and eventually accumulate mold. This restricts airflow and causes additional condensation to collect on the evaporator coils, creating a humid environment where mold and mildew thrive. Dirty water can also freeze on the evaporator coils, producing an unpleasant musty smell from your air conditioning unit.

Depending on the type and efficiency of your air filter, you should replace it approximately every 90 days. Swapping out your air filter is easy. Consult with your owner’s manual to determine the right air filter replacement model and size, and then:

  • Locate the filter: HVAC system air filters are usually located in a ceiling vent or between the unit and the return duct. 
  • Disconnect the power: Turn off the A/C system from the breaker switch to prevent it from absorbing debris and to minimize electrical hazards.
  • Remove the filter: Loosen the vent fastenings and pull out the old filter. 
  • Replace the filter: Insert the new filter with its arrow pattern pointing away from you. Replace the vent cover and turn the power back on to the unit.

An HVAC technician can replace your air filter during routine maintenance or other service calls. If you suspect the evaporator coils are moldy, frozen, or both, it’s time to schedule maintenance.

How to Get Rid of the Smell in Your Air Conditioner

Annual AC maintenance is essential for a fresh-smelling home. 

After Amarillo’s chilly winters, spring is the best time to schedule your tune-up, which will include a thorough A/C cleaning and duct inspection, which can help identify moisture issues before they become a problem for your health and your home. Your friendly technician will replace your air filter and leave you with a supply for the cooling season. Staying on top of preventative maintenance allows your system to perform effectively and efficiently, saving energy costs and promoting a healthier indoor environment.

What To Do if Your AC Smell Won’t Go Away: Call Frank’s!

Nobody likes a musty smell circulating throughout their home, especially when it may be caused by mold, which reduces your indoor air quality and can reduce the efficiency of your system and lead to higher utility bills. If your air conditioner smells musty, give us a call at Frank’s Repair Plumbing. We’ve been serving the Amarillo area for more than 70 years, and our friendly, knowledgeable technicians are happy to address your HVAC concerns and prevent future issues. Contact us today and learn why we’re the go-to choice for HVAC services in the Texas Panhandle.