ac smells mustyStale, dank, and pungent odors aren’t just annoying; they’re potentially dangerous. They’re the result of mold, mildew, and bacterial growth, and when they’re emitted by your AC, they can lead to serious respiratory problems. In most cases, musty AC smells are the result of a breakdown in your cooling system. While you won’t be able to fix them without the help of an HVAC technician, knowing why your AC smells musty may help you diagnose the problem, so you can guide the technician when he arrives. The most common causes are:

Full Drain Pan

Air conditioners have two primary components: the evaporator coils, which absorb heat, and the condenser coils, which expel it. Because the evaporator coils are significantly cooler than the surrounding air, they create condensation, like a cool glass on a hot day.

As condensation accumulates, it drips off the coils and into the drain pan, one of the safeguards designed to remove excess moisture from your AC. The pan is supposed to drain water into the ground or sewage line, but if it becomes clogged, the water can overflow and become stagnant, an ideal environment for mold and bacteria.

Blocked Condensate Line

Condensate lines funnel moisture out of your air conditioner, usually through an exterior wall or your home’s plumbing system. However, because the line is narrow, it only takes a small amount of dirt, dust, or algae to clog it. Clogged condensate lines not only increase your risk of corrosion but mold and mildew as well.

Frozen Evaporator Coils

Evaporator coils require airflow to absorb heat. If airflow becomes restricted, due to a faulty fan or dirty coils, condensation starts to freeze instead. Once the coils are coated in ice, the air inside your AC becomes damp, which encourages mold in the dark environment.

Dirty Filter

Filters trap dust, dirt, and other debris before they can be blown out into your home. However, if they aren’t changed regularly, they can become saturated with grime, the perfect habitat for mold and bacterial colonies. The good news is that replacing dirty filters does not require professional assistance. Replacement filters are available at most local hardware stores and can be installed without any special training.

Moisture in Air Ducts

There are several ways for water to get into your air ducts. Humid air can seep in through holes, cracks, and loose seams. A clogged condensate line can trap moisture in your AC, allowing it to circulate through your home rather than draining away. Finally, if your air conditioner hasn’t been properly sized, it may cycle air too quickly, before dehumidifying. If musty smells appear as soon as you turn on your AC, before any noticeable temperature drop, moldy ducts are the most likely cause.

Poorly Sized AC System

An air conditioner that’s too large can lead to problems. While a large AC cools your home quickly, it also moves air through your system before all the moisture can be extracted. As a result, water builds up inside your air conditioner, leading to mold and bacterial growth. If you’re worried your AC may be too large, have it sized by an HVAC technician.

Protect Your Cooling Systems

Agway doesn’t just power your air conditioner, we protect it with our EnergyGuardTM program. Repairing your AC system can cost thousands, but Agway customers are protected because they’re enrolled in EnergyGuardTM as soon as they join, which means that when their AC breaks down, our customers don’t pay out of pocket for the majority of repairs. We shoulder the cost of the repairman and all covered parts. There are no service fees or deductibles. So what are you waiting for? Sign up today and save!