why does my windshield fog up?
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  1. #1
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    why does my windshield fog up?

    As the title states my windshield fogs up almost every time i drive at night, during the day it probably does too but not enough to bother me...only way to get rid of the fog/condensation is to crank up the a/c towards the upper vents/defrost; it works and clears it up in a few seconds, then if i turn it off it will immediately fog up again...what gives?? does my interior cabin filter need a cleaning? ive tried to windex my windshield all i got was black tar looking stuff (i assume from the cigarettes)

    anyone else have the same problem?

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  3. #2
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    Mine fogs up a lot more than any other car I've owned or driven... not sure what the deal is.

    Do you hear gurgling in the dash / smell coolant ever?

  4. #3
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    rain x has stuff for fog i believe. Or, try getting anti fog spray, usually used for bathroom mirrors.

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    If it's daily you have a leak in your heater core...and that's gonna SUUUUUCK to replace. If it was normal condensation it would clear up very quickly and only happen when it's very cold or humid out.

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    Quote Originally Posted by quality_sound View Post
    If it's daily you have a leak in your heater core...and that's gonna SUUUUUCK to replace. If it was normal condensation it would clear up very quickly and only happen when it's very cold or humid out.
    I agree

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    Quote Originally Posted by gab5 View Post
    As the title states my windshield fogs up almost every time i drive at night, during the day it probably does too but not enough to bother me...only way to get rid of the fog/condensation is to crank up the a/c towards the upper vents/defrost; it works and clears it up in a few seconds, then if i turn it off it will immediately fog up again...what gives?? does my interior cabin filter need a cleaning? ive tried to windex my windshield all i got was black tar looking stuff (i assume from the cigarettes)

    anyone else have the same problem?
    we drove our Passat in Atlanta for 5 1/2 years, and NEVER experienced the type of interior fogging you are referring to. I'm thinking the smoking may be the difference, as our car has never been smoked in.

    Try some of the products that other posters have suggested on the windshield, maybe that will help.

    The condition you describe is NOT NORMAL for Atlanta on a regular basis (you probably know that), and I lived there for 55 years.

    BTW, I once bought a used car that had obviously sat on the lot in the elements for a while. Windshield looked fine during the day, but was dreadful at night, particularly when raining - you couldn't see crap. Turned out to be a really filthy windshield that normal glass cleaners couldn't help. I had a glass company buff the windshield with a buffer and some special cleaners, and I used some 0000 steel wool and a special cleaner (sorry dont remember what - it was over 10 years ago), and that cleared it right up.

  8. #7
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    Quote Originally Posted by macaddiict View Post
    Mine fogs up a lot more than any other car I've owned or driven... not sure what the deal is.

    Do you hear gurgling in the dash / smell coolant ever?

    no never hear any gurgling, nor do i smell coolant....weird

  9. #8
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    Quote Originally Posted by Cloud View Post
    rain x has stuff for fog i believe. Or, try getting anti fog spray, usually used for bathroom mirrors.
    i might have to look into that....but as with most other rainx products is it true that if you stop using them it causes more damage in the long run then before you even started using the product???

  10. #9
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    ok...probably not the source but I'll mention it....Are you sure your vent is open? If the vent is closed then it fogs up real fast.

  11. #10
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    You might want to check all of your carpets for dampness. It's possible that you have one of the infamous Passat leaks (either sunroof, A/C condensate, or cowl drains). Lift all four of your floor mats and feel around to make sure everything is dry.

  12. #11
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    Quote Originally Posted by gab5 View Post
    i might have to look into that....but as with most other rainx products is it true that if you stop using them it causes more damage in the long run then before you even started using the product???
    the rainx stuff is good however if you dont apply it correctly there is a haze that builds up and is worse then condensation at night.

  13. #12
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    Quote Originally Posted by gab5 View Post
    As the title states my windshield fogs up almost every time i drive at night, during the day it probably does too but not enough to bother me...only way to get rid of the fog/condensation is to crank up the a/c towards the upper vents/defrost; it works and clears it up in a few seconds, then if i turn it off it will immediately fog up again...what gives?? does my interior cabin filter need a cleaning? ive tried to windex my windshield all i got was black tar looking stuff (i assume from the cigarettes)

    anyone else have the same problem?
    When you drive at night do you have the AC on? Do you have the setting to recirculate? Is the window fogging up on inside (which I suspect) or outside? My guess is you are on recirculate without any AC on, when you turn it to defrost it reverts to fresh air, and the compressor dries out the air. Try driving at night with AC on, not on recirculate, and adjust the temp via dial so you are not getting ice cold air.

  14. #13
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    yes, that's what I meant when I mentioned (above) vent open vs. vent closed(recirculate) . It should not be on recirculate ie...the vent should be open.

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    Quote Originally Posted by macaddiict View Post
    Mine fogs up a lot more than any other car I've owned or driven... not sure what the deal is.

    Do you hear gurgling in the dash / smell coolant ever?
    I fog up easily on cold or humid mornings and very occasionally hear gurgling. Never any smell of coolant. Been that way since I got the car, never thought anything about it. Why did you ask, what does this mean? (panic)

    Of course, I am off warranty now!

  16. #15
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    Gurgling isn't that big a deal. The heater core is behind the dash and the gurgling is nothing to worry about unless you smell coolant as well.

  17. #16
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    I had this problem on my Mercury Mystique, so bad in fact that it would fog over the whole windshield going down the road completely blind.
    Turns out the water was not draining properly from inside the condensor / heater core area. The little rubber nipple that hangs out the bottom of the car was stuck shut. Check the drainage to see if it's working properly. Temporary problems like this are no big deal but gone unchecked, it can lead to mold build up inside the air / heater core area. That can be a real pain the ass. It stinks real bad and usually requires professional cleaning solutions to resolve. Also check your pollen filter to make sure enough air is getting in.

  18. #17
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    I have had a problem with for on the OUTSIDE of the windshield with the AC on. A swipe of the wipers would erase the spot right in front of the vents. It seems that the AC was so cold that it would cool the exterrior glass below the dew point of the outside air and ... fog!

    that's what you get for living in the south!

    JO

  19. #18
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    Quote Originally Posted by ytqm View Post
    When you drive at night do you have the AC on? Do you have the setting to recirculate? Is the window fogging up on inside (which I suspect) or outside? My guess is you are on recirculate without any AC on, when you turn it to defrost it reverts to fresh air, and the compressor dries out the air. Try driving at night with AC on, not on recirculate, and adjust the temp via dial so you are not getting ice cold air.

    yea i have the ac on and the vent to the top/defrost setting, with it on the defrost setting it automatically turns off the recirculate and goes to fresh air...and yea if it is set to cold it clears up really fast but then it frosts the outside of the windsheild up, and i have to turn the wiper on a couple times to clear it up, if i turn to warmer temp it works less effecient.

  20. #19
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    Quote Originally Posted by JohnOrganic View Post
    I have had a problem with for on the OUTSIDE of the windshield with the AC on. A swipe of the wipers would erase the spot right in front of the vents. It seems that the AC was so cold that it would cool the exterrior glass below the dew point of the outside air and ... fog!

    that's what you get for living in the south!

    JO
    ditto on that note, when i turn the ac on to clear it up the outside gets a piece of frost/condensation so i have to turn the wipers on to clear that up

  21. #20
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    Quote Originally Posted by Altair 4 View Post
    You might want to check all of your carpets for dampness. It's possible that you have one of the infamous Passat leaks (either sunroof, A/C condensate, or cowl drains). Lift all four of your floor mats and feel around to make sure everything is dry.
    yea i had a sunroof leak about a year ago, i had to pinch the little rubber plug thinggy between the drivers door and the frame but i havent checked it since, i got monster mats now so i didnt really noticed any water or damp carpets or even bothered to check for that. ill go do that tonight when it stops raining

  22. #21
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    Quote Originally Posted by AndreasPassat View Post
    ..... The little rubber nipple that hangs out the bottom of the car was stuck shut. Check the drainage to see if it's working properly. Temporary problems like this are no big deal but gone unchecked, it can lead to mold build up inside the air / heater core area. That can be a real pain the ass. It stinks real bad and usually requires professional cleaning solutions to resolve. Also check your pollen filter to make sure enough air is getting in.
    where is this little rubber nipple? anyone have a pic pointing it out? i know where the one between the door and frame is but i didnt know there was another under the car?

    ...or are you referring to your Mercury?

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    Quote Originally Posted by gab5 View Post
    where is this little rubber nipple? anyone have a pic pointing it out? i know where the one between the door and frame is but i didnt know there was another under the car?

    ...or are you referring to your Mercury?
    there are 2 more in the trunk behind the side covers. pull those doors off and look for the green tubes. those are the rear drains.

  24. #23
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    I think your windshield could be dirty too - that doesn't help - wash it 3 times with Windex or Straight Vinegar at first if you can to cut off any film.

    All other suggestions for moisture are right on. These cars are notorious for water intrusion in many areas.

    Good Luck.

  25. #24
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    Quote Originally Posted by gab5 View Post
    where is this little rubber nipple? anyone have a pic pointing it out? i know where the one between the door and frame is but i didnt know there was another under the car?

    ...or are you referring to your Mercury?
    I was referring to Mercury, but the Passat has drain nipples placed in strategic locations for water drainage. At this point in time I don't where they are for a/c condensation drainage.

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