My Aunt had the same problem with hers. She found out that if you leave the A/C button on regardless of if you are using hot or cold air that it will defog your window. A/C actually stands for Air Circulation and not Air Conditioner. The rain X products work ok but when it comes time to reaply the product you should clean your window with vinager and newspaper so that it does not leave a film which would worsen the problem.