I heard Pat Guass form Motor Week talking about this. He said the smell is usually caused by mold in the a/c. His recommendation was to get a can of Lysol, turn on the a/c and spay the lysol into the outside air vents. These vents are between your hood and windsheld on the outside of the car. This way the lysol will enter the a/c and kill the mold and provide a plesant smell. Hopes that helps.