What causes a windshield to fog?
Heat will cool off and cold will heat up at the same rate of time. When there is an imbalance of temperature between the inside and outside of the windshield glass, vapor will form on the glass until a balance of temperature is restored.
There are many products on the market which can prevent this from occurring. One of the easiest ways to prevent this is to coat the glass with shaving cream, let it dry and buff it off. This also works on the mirrors in your bathroom.
Your window is probably not fogging up on the inside. When the ambient relative humidity is high and the Touareg’s air conditioner is engaged, cold air blows on the windshield causing the temperature of the glass to drop below the ambient dew-point. When this happens, condensation forms on the outside of the windshield. You can clear this condensation using the windshield wipers. Touareg owners have reported that this condition only occurs when cold air is directed through the large mesh vent in the middle of the dashboard. By manually selecting the ‘lower vent’ setting on the climate control system, you can prevent air from b lowing from this mesh vent thereby reducing the amount of condensation that forms.
