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it's really not that complicated, you just have to understand why condensation is happening in the first place. it's always because the glass is colder than the moist air it is touching. there are two strategies to deal with this: either blow air with very low relative humidity over the glass, or fix the temperature differential itself. if you're using the "blow dry air" strategy, you always want to turn on AC and at least some heat, as this will create low relative humidity.

now in the winter you can sometimes do better than this by fixing the temperature differential itself. you can either lower the windows or cool the entire interior by blowing air with no heat. in reality, most people don't actually want to drive around in the winter with windows down or no heat, so the best tolerable option is usually to do as above: turn on AC and heat.

in the summer you can also get fogging on the outside of the windows. just use your wipers for this.




>it's really not that complicated

After reading this I am still not sure which one to use. They seem to both work.


Both work, one is just faster than the other. The post you replied to seems to imply that cold air is better in the winter, but that is absolutely not my experience.

When I get in the car in the morning, the air is already cold. No amount of more cold air from the vents will clear that. What's making it fog up, is the moisture I'm exhaling. More cold air is not going to fix that unless I drive with all windows down. So the only reasonable option since AC don't work at low temperature, is waiting for the car to heat up.


tl;dr of my post: turn on AC and blast hot air at the windshield. if that doesn't work in the winter, open your windows. if it doesn't work in the summer, it's because the fog is on the outside of the windshield; use your wipers.




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