Your air conditioning may smell musty due to condensation that builds up on the cold components inside of your dash. These cold components can collect dust out of the air. Over time the dust will build up, and combined with the moisture this will cause a musty smell. This musty smell is coming from mold and mildew from the dust. One way to prevent this from happening is to always run your air conditioning on recirculate. This will prevent the dust from entering the cab of your vehicle. We also recommend having your cabin air filter changed. Your cabin air filter collects the spores, pollen, and dirt from the air in your cab. Give us a call and let us take care of you.