Do you keep the ventilation on with all vents open? My car used to get quite damp inside, through the winter I drive to work in the dark, it sits in the shade all day then I drive home in the dark, so it never saw any sunshine for a few months. Parking it in the sun at work helped.


Check the spare wheel well for a puddle of water,


Keep the air conditioning switched on when in the car, it will pull all the moisture out the air, and make sure you haven't got the air recirculate switched on.