Windows Fogging
Thread Starter
Pro
Joined: Apr 2013
Posts: 505
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From: MN
Windows Fogging
Anyone else run into the problem of the entire car fogging up badly when the humidity is high ? Maybe it's just because the volume inside a 911 is so much smaller than in a larger car, but it sure seems sensitive. Have to blast the defrost just to defog the windows.
Rennlist Member
Joined: Oct 2014
Posts: 6,942
Likes: 1,291
From: L.I. NY
Yup! Mine does it too. I think it has to do with the foam covering on the Defrost/Heater/Vent flap in the air exchanger unit. Mine is a high milage (for a 911 - 1999/142,000 mi.) car that has seen plenty of use through the years. The foam covering on the diverter flap decomposes over time which exposes large holes in the flap which in turn leads to high moisture air entering/re-entering the cabin when it shouldn't be... I'm not sure of this, and it may be way off line, but I'm going to open things up this winter to see if my foam is indeed gone...
Banned
Joined: Jan 2013
Posts: 26,140
Likes: 5,464
From: Chicagoland Area
Don't recycle the cabin air, and keep your interior windows very clean. Both help.
Window cleaning tips:
*dedicated glass only 100% cotton terry towels, no fabric softener
*mix in spray bottle 1 part denatured alcohol to 2 parts distilled water
*spray towel, wash glass, buff dry with second towel
Window cleaning tips:
*dedicated glass only 100% cotton terry towels, no fabric softener
*mix in spray bottle 1 part denatured alcohol to 2 parts distilled water
*spray towel, wash glass, buff dry with second towel
Rennlist Member
Joined: Mar 2014
Posts: 318
Likes: 99
From: Connecticut
LexVan is spot on. Recirculated air does not dehumidify and will condense on the windows - more so if they are dirty. I often see loaded cars fogged up on the inside during the winter for this very reason.
Race Director
Joined: Sep 2006
Posts: 19,031
Likes: 266
From: Bentonville, AR
Couple of things: 1) Be sure the body water drains are clear. The ones under the front trunk lid especially. If these are not clear they can retain water and this can add to the humidity -- at least initially -- the A/C system pulls into the cabin. While I am on the subject be sure the cabin is dry. Check the carpets on the floor and along the door bottoms. I found the passenger side door bottom carpet wet on my Boxster the other day and the problem appears to have been a door membrane that was not sealed properly.
2) If you use the A/C try to remember to a few miles/minutes before your final destination to turn off the A/C and just let the cabin vent fan run to dry some of the moisture from the system. If you don't do this upon restart the moisture that was present can result in a sudden fogging of the car's windows. 'course, some times when one does this the glass starts to fog up again so you have to "time" this so you maximize the drying time without running into a fogging window problem.
3) Be sure the cabin air filter is not real dirty and is installed correctly and is not damp.
4) I have found the inside glass surface develops a film of a mixture of I guess fine dust and who knows what else. (I do not smoke and no one else smokes in my cars.) Even though I practice (1), (2), and (3) above occasionally it seems the fogging problem gets worse and then I clean the windows and things are better. In my area about twice a year is par for the course for interior glass cleaning but depending upon where you live/drive you may need to do this more (or less?) often.
Rennlist Member
Joined: Oct 2014
Posts: 6,942
Likes: 1,291
From: L.I. NY
Sometimes.
Couple of things: 1) Be sure the body water drains are clear. The ones under the front trunk lid especially. If these are not clear they can retain water and this can add to the humidity -- at least initially -- the A/C system pulls into the cabin. While I am on the subject be sure the cabin is dry. Check the carpets on the floor and along the door bottoms. I found the passenger side door bottom carpet wet on my Boxster the other day and the problem appears to have been a door membrane that was not sealed properly.
2) If you use the A/C try to remember to a few miles/minutes before your final destination to turn off the A/C and just let the cabin vent fan run to dry some of the moisture from the system. If you don't do this upon restart the moisture that was present can result in a sudden fogging of the car's windows. 'course, some times when one does this the glass starts to fog up again so you have to "time" this so you maximize the drying time without running into a fogging window problem.
3) Be sure the cabin air filter is not real dirty and is installed correctly and is not damp.
4) I have found the inside glass surface develops a film of a mixture of I guess fine dust and who knows what else. (I do not smoke and no one else smokes in my cars.) Even though I practice (1), (2), and (3) above occasionally it seems the fogging problem gets worse and then I clean the windows and things are better. In my area about twice a year is par for the course for interior glass cleaning but depending upon where you live/drive you may need to do this more (or less?) often.
Couple of things: 1) Be sure the body water drains are clear. The ones under the front trunk lid especially. If these are not clear they can retain water and this can add to the humidity -- at least initially -- the A/C system pulls into the cabin. While I am on the subject be sure the cabin is dry. Check the carpets on the floor and along the door bottoms. I found the passenger side door bottom carpet wet on my Boxster the other day and the problem appears to have been a door membrane that was not sealed properly.
2) If you use the A/C try to remember to a few miles/minutes before your final destination to turn off the A/C and just let the cabin vent fan run to dry some of the moisture from the system. If you don't do this upon restart the moisture that was present can result in a sudden fogging of the car's windows. 'course, some times when one does this the glass starts to fog up again so you have to "time" this so you maximize the drying time without running into a fogging window problem.
3) Be sure the cabin air filter is not real dirty and is installed correctly and is not damp.
4) I have found the inside glass surface develops a film of a mixture of I guess fine dust and who knows what else. (I do not smoke and no one else smokes in my cars.) Even though I practice (1), (2), and (3) above occasionally it seems the fogging problem gets worse and then I clean the windows and things are better. In my area about twice a year is par for the course for interior glass cleaning but depending upon where you live/drive you may need to do this more (or less?) often.
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Burning Brakes
Joined: May 2015
Posts: 890
Likes: 1
From: Jacksonville, FL
Sometimes.
Couple of things: 1) Be sure the body water drains are clear. The ones under the front trunk lid especially. If these are not clear they can retain water and this can add to the humidity -- at least initially -- the A/C system pulls into the cabin. While I am on the subject be sure the cabin is dry. Check the carpets on the floor and along the door bottoms. I found the passenger side door bottom carpet wet on my Boxster the other day and the problem appears to have been a door membrane that was not sealed properly.
2) If you use the A/C try to remember to a few miles/minutes before your final destination to turn off the A/C and just let the cabin vent fan run to dry some of the moisture from the system. If you don't do this upon restart the moisture that was present can result in a sudden fogging of the car's windows. 'course, some times when one does this the glass starts to fog up again so you have to "time" this so you maximize the drying time without running into a fogging window problem.
3) Be sure the cabin air filter is not real dirty and is installed correctly and is not damp.
4) I have found the inside glass surface develops a film of a mixture of I guess fine dust and who knows what else. (I do not smoke and no one else smokes in my cars.) Even though I practice (1), (2), and (3) above occasionally it seems the fogging problem gets worse and then I clean the windows and things are better. In my area about twice a year is par for the course for interior glass cleaning but depending upon where you live/drive you may need to do this more (or less?) often.
Couple of things: 1) Be sure the body water drains are clear. The ones under the front trunk lid especially. If these are not clear they can retain water and this can add to the humidity -- at least initially -- the A/C system pulls into the cabin. While I am on the subject be sure the cabin is dry. Check the carpets on the floor and along the door bottoms. I found the passenger side door bottom carpet wet on my Boxster the other day and the problem appears to have been a door membrane that was not sealed properly.
2) If you use the A/C try to remember to a few miles/minutes before your final destination to turn off the A/C and just let the cabin vent fan run to dry some of the moisture from the system. If you don't do this upon restart the moisture that was present can result in a sudden fogging of the car's windows. 'course, some times when one does this the glass starts to fog up again so you have to "time" this so you maximize the drying time without running into a fogging window problem.
3) Be sure the cabin air filter is not real dirty and is installed correctly and is not damp.
4) I have found the inside glass surface develops a film of a mixture of I guess fine dust and who knows what else. (I do not smoke and no one else smokes in my cars.) Even though I practice (1), (2), and (3) above occasionally it seems the fogging problem gets worse and then I clean the windows and things are better. In my area about twice a year is par for the course for interior glass cleaning but depending upon where you live/drive you may need to do this more (or less?) often.
Bingo! Those pesky drains will do it. I think that the amount of moisture that is inside of the car is much more than would be "hitching a ride" on the air. Look for water incursion inside of your car.
Thread Starter
Pro
Joined: Apr 2013
Posts: 505
Likes: 51
From: MN
Thanks for the feedback. Everything inside the car is dry. I've tried turning the ac off with a few miles left to drive, but this doesn't seem to do the trick and I agree that the ac should actually dry things out. I have had a lot of the black foam which has degraded come out of my air vents, so maybe there is something related to this. I like the idea of checking the drain areas, since this seems to make the most sense, especially since this seems to happen more after it's rained.
Drifting
Joined: Sep 2001
Posts: 2,467
Likes: 16
From: redmond wa
But... Ask yourself.. What happens once the A/C is shut down, manually or automatically (OAT declines below 35dF) with the condenser CLOGGED with condensate.
Best not to use A/C except for summertime cooling needs. HEAT will always clear the windshield of condensate.
A/C dehumidifying capability depends on dewpoint and OAT.
As OAT declines below ~45dF A/C dehumidifying capability declines, non-existent below 32dF.