Why Does My Air Conditioner Smell Musty? (Answered)

A musty smell from your air conditioner often indicates mold or mildew growth within the system, typically caused by excess moisture or poor ventilation. Clogged filters, leaky ducts, or dirty cooling coils could also contribute to this issue. Regular maintenance can help prevent this.

How Does Mold Growth Contribute to Musty Smell?

Mold growth on an air conditioner’s evaporator coil is often responsible for producing musty air conditioning odor. This happens as condensation collects inside your home during air conditioning operation and clogs up air flow, leading to poor cooling performance and poorer indoor air quality. A good way to identify mold in this situation is smelling the air; oftentimes there will be an unpleasant musty aroma when there is mold on an evaporator coil.

Can a Blocked Drain Line Cause Musty Odor?

Musty odors emanating from an air conditioner could also be due to a blocked drain line. As your air conditioning system draws moisture from the humidity in your home, the collected water is collected in a drip pan before being sent through a small drainage pipe to drain outside. Unfortunately, this dark, humid place provides ideal conditions for algae growth which clogs the drain line resulting in stagnant water which causes musty odors within your house and decreases the efficiency of your AC.

How Can I Clean a Blocked Drain Line?

If your air conditioning has an unpleasant musty odor, turn off all power at the panel and breaker box before searching for and locating its drain line (in single-family homes this will typically be near the condenser unit; in apartments/condos it might be in the water heater closet).

If it appears plugged up, turn off your AC, remove its cap, remove any visible gunk, then pour a cup of bleach down its drain to clear it (be sure that all power has been disconnected prior to pouring bleach as this could potentially clog it further). To access it safely with ladder access (use caution!), locate its drain line (in single-family homes this should be near condenser unit; in apartments/condos it might be in water heater closet). If its full, turn off its power as soon as it could plug it up!

What Other Factors Could Lead to a Musty Smell?

Other causes for an air conditioning’s musty odor could include pest infestation, broken fan belts or an improper compressor installation. A musty scent from your air conditioning could even come from dead animals that have fallen into its unit – making this an easy issue to solve by pest-proofing your AC with tight seals and keeping an eye out for signs of rodent activity in its vicinity.

How to Deal With Possible Pest Infestation?

If you suspect there may be dead animals inside of your AC unit, contact a pest control company immediately. Their technician can help identify and remove them as soon as possible and also offer advice about how to prevent insects or mice from getting inside again in future.