[drcoastline]

Mold spores are present everywhere and you can not kill it. You can eliminate it on a surface as 962 did. But it is still present and the spores will come back.

Mold needs four things in order to grow. A food, moisture, warmth and oxygen. Remove any one of the four and the mold will not grow. In this case the food source is the leather. There are other food sources present in cars as well. carpeting, door cards, sound deadening, paper items in the glove box, etc.. Any organic material. We know we can not remove those things so we need to remove one of the others.

Oxygen will be hard to remove with out placing the car in a vacuum sealed bag.

You could regulate the heat but the easiest to regulate is the moisture/humidity. A simple air conditioner or dehumidifier will do the trick. An air conditioner is a dehumidifier. Regulating the moisture/humidity will also help regulate the heat. Removing or regulating the moisture will also help with rust and wire corrosion.