Odor

When an air conditioner has an odor, you will notice it most when the unit is running and blowing cool air into your house. The odor that accompanies the air tends to be musty or earthy. It will remind you of damp basements. You might also smell this odor when you are near your air conditioning vents even when the air is not running.

Cause

The cause of the odor in the air conditioner is a problem called odoriferous coil. It occurs when mold grows on the condenser coil inside the air conditioner. When the air runs, the unit blows the odor of mold and mold spores into your home.

Solution

Removing the mold will get rid of the odor. Clean the coil with a solution of 1/2 cup of bleach in 1 gallon of water. Make sure the air conditioner drains properly, which will reduce moisture buildup and make it less likely that the mold will return. You may need to replace the air filters in your home. They can trap the musty smell and recirculate it into your house.