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Discussion Starter #1
Every time I switch my air con off, the window mists up at the bottom of the windscreenits the summer, the car is bone dry and kept in a garage over night.

What can I do to purge the system of humidity? leave it off for a week or so with a fast fan?

I normally leave air con on 100% just to keep the window clear.

any help would be greatly appreciated.

Alex.
 

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This happens to me when I have the air recirculating rather then drawing in fresh air from the outside. It's come up a few times on here and it's always been the cause.
Edited by: Grant25
 

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What Grant said. When you have the aircon on, you must switch the lever to recirculation, rather than fresh air. It's more efficient, and the aircon system isn't continually drawing in external humid air and blasting it against a hot windscreen, where it will condense until the temp of the glass drops.
 

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It is normal this will happen on expensive cars too.
 

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I'm confused. I don't know if Dan agrees or disagrees with Grant. If having the air recirculating when the air conditioning is on is a "must" why does it not say so in the manual?Edited by: Beevee
 

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Discussion Starter #6
I'm also confused.. How do I stop the misting with the air con off? I'm wondering if its just going to take a while for all the moisture in the system, where ever that is to go away.
 

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To clear the system you need to run it with air-con off and FULL heat on for a while. This will help evaporate any residual moisture in the system.

It also helps kill off any spores, which can then go on to make the system smelly.
 

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I must admit I never turn my air conditioning off and have never had trouble with windows misting up.
 

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Sorry if my post wasn't clear when running the air con make sure you are drawing in fresh air NOT recirculating.

And if you switch the ac off the windows will mist up as the moisture the ac was drawing out re enters the car. Best to just turn it now to 1 or up on the temp a little if your getting a bit nippyEdited by: Grant25
 

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Sorry, misread Grant's post, but I still maintain that running the aircon on recirculate if better to stop misting, as the outside air is usually more humid than that in the car, and therefore will condense when chilled through the aircon system, then blown onto a hot/warm surface such as the windscreen.

You will find that the aircon is MUCH more efficient when on recirculate, as it is constantly chilling air that has already passed through the aircon system, therefore each pass will cool it further until the minimum temp is achieved, whereas on fresh air setting, the system is constantly pulling in warm/hot air from outside and trying to cool that instead.

It's a bit like taking water from a fridge, and water from a boiled kettle, and making ice cubes from them both. The water from the fridge will freeze before the water from the kettle, since the temperature difference is much less.
 

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If you read the manual you will find that VW recommend that the air conditioning should be left on at all times. They also recommend that recirculating mode should only be used briefly when the outside temperature is very high. I see no reason to ignore this advice. You should normally allow fresh air to enter the vehicle otherwise you are recirculating stale air which could lead to drowsiness. VW also warn against using recirculating function when in demist mode. Edited by: Beevee
 

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shakotanVIP said:
Sorry, misread Grant's post, but I still maintain that running the aircon on recirculate if better to stop misting, as the outside air is usually more humid than that in the car, and therefore will condense when chilled through the aircon system, then blown onto a hot/warm surface such as the windscreen.

You will find that the aircon is MUCH more efficient when on recirculate, as it is constantly chilling air that has already passed through the aircon system, therefore each pass will cool it further until the minimum temp is achieved, whereas on fresh air setting, the system is constantly pulling in warm/hot air from outside and trying to cool that instead.

It's a bit like taking water from a fridge, and water from a boiled kettle, and making ice cubes from them both. The water from the fridge will freeze before the water from the kettle, since the temperature difference is much less.
Warm water freezes faster than cold (Mpemba effect)
 

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Discussion Starter #13
Thanks for all the advice. I will run it hot and off for a while. I must admit, it does pong sometimes.
 

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I know you believe you understand what you think I said. I am not sure what you heard is what I meant �®�®
 

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Beevee said:
I know you believe you understand what you think I said. I am not sure what you heard is what I meant �®�®

Surely what he believes he heard is what he's not sure if he understood what he thinks you said that he meant?
 

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Discussion Starter #16
Huhhh? Lol
 
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