Can a Car Heater Blower Create More Window Condensation?


The short answer is yes, there are times when using the ventilation system can create more windshield condensation. The real question is why it happens, and there are two primary causes for this. Both revolve around humidity, or excess moisture.


External Moisture

The first is an external issue in which the air outside is especially humid or moist. Some examples would be:

  • Autumn and winter
  • Areas with naturally high humidity
  • Locations near large bodies of water such as lakes or oceans


Dry warm air is good to have in both hot and cold seasons. In winter, it helps melt away frost and fog. In autumn and winter, humid air can cause flash fogging when in contact with the cold windshield, which has been cooled by the outside air. This is especially hazardous early mornings when the sun has not yet warmed up the car interior.Therefore the ventilation system can best be set to ‘recirculation’


Internal Moisture

External moisture is more situational or seasonal – those who experience it often, know how to handle the situation. The above tips are good to know for travelers as well. Problems caused by internal moisture, however, can happen nearly anywhere, at any time. Moisture that has settled inside your vehicle can cause frosting on the inside of the windows. This buildup of moisture doesn’t necessarily be due to rain either.