It can be shocking to turn on your air conditioner and realize your HVAC smells musty. Your air conditioner blows foul or unpleasant-smelling air, which can quickly make your living conditions uncomfortable. In some cases, these bad smells can indicate a severe problem, but most of the time, it’s a quick fix that could have been prevented with air conditioning unit maintenance.

Why Does My Air Conditioner Smells Musty?

Dirty Evaporator Coil

An AC unit’s evaporator coil is responsible for absorbing heat from indoor air so that the blower fan can circulate cooler air throughout the property. For the heat exchange to occur, air must flow over the coil. The refrigerant inside the component is what attracts the heat.

Indoor air often contains many airborne pollutants like pollen, pet dander, and dust. Though the air conditioner’s filter will trap particles, dust and debris can still accumulate on the coil. Unless you change or clean the filter every one to three months, the dirty filter can become a breeding ground for mold.

Mold and mildew usually have a musty odor. These fungal growths thrive in dark, warm environments, making the evaporator coil inside a prime place for mold to grow.

Condensate Drain Line is Clogged

You know this is the reason behind your mold or mildew problem when the air conditioner automatically shuts down after working for a short while. This happens because water flows over the condensate pan that triggers an emergency shut off. Another sign of a clogged condensate drain line is water pooling in the inside unit.

Excess condensation forming over the evaporator coil causes water to drop into the drain pan. It then exits out of the drain line. Clogged drain line because of dirt or debris causes the condensation water to get backed up in the drain pan. Mold can easily grow in such circumstances. It has moisture, food, warm temperature, and darkness to flourish.

Mold or Mildew in The Duct Work

If water pools or condensation builds inside the duct work, it can become the perfect environment for mold to grow. Dark, damp, and dirty, duct work that hasn’t been cleaned will grow mold – and then spores from the mold will be blown down into your home by the air conditioner’s fan. The build-up of dust, dirt, and mold in the ducts can lead to irritation and allergic reactions in the people who are breathing the air in your home. That’s why your air conditioner smells musty.