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  #11  
Old 10th February 2016, 03:56 PM
mattylondon mattylondon is offline
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I also get some condensation on the rear window. It doesn't happen when raining only when the temperature drops. I've double checked there are no leaks and the seals are good. So I've put the problem down to the fact that the A8 is highly sealed and doesn't allow many air changes to give proper ventilation when parked up. As a crude calculation of only 1 air change per hour we would need about 5000litres of air movement, which I doubt the A8 achieves. Ideally 4 changes per hour would be needed. Also it depends on the relative humidity within the cabin. So if there are HVAC drain problems it will exaggerate the condensation problem because the dew point will be higher inside the cabin.
In my old A4 I used to leave the sun roof open ever so slightly, even when it rained, and that car was dry as a bone with zero condensation problems. Sadly my '8 doesn't have a sun roof.
From what I know in the building industry a highly sealed environment with poor ventilation is a breading ground for condensation problems and then worse, as Mike discovered in his S8.

Edit:
Do you have the ski hatch into the boot? Try leaving this open and the boot side panels removed to encourage more air changes as behind the rear bumper there are two 'hit and miss' vents. It's worth a try to see if it lessens the condensation
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Last edited by mattylondon; 10th February 2016 at 04:36 PM.
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  #12  
Old 10th February 2016, 04:25 PM
kele kele is offline
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I also had a leak on the top near side of the rear screen. It was fine unless it was raining! It was only if it rained that I got condensation and actually water drips.

Seemingly seals are not covered under the 'comprehensive' audi used approved warrentee. So the answer was a new screen. That was over 2 years ago now. It's been fine since....
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  #13  
Old 10th February 2016, 04:42 PM
Lee S Lee S is offline
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Yeah. I put it down to condensation inside the vehicle. I have been doing a lot of loading/unloading, baby-in/baby-out movements over the last few weeks when it has been hammering down, so a bit of sun (like today) will heat the cabin up a bit and the moisture in the air condenses on the screen. Not sure why just in that corner though. I also have a bit of condensation in the rear light lenses but again only on the right hand side. I wonder if there is a build up of moisture behind the battery area.

I wonder if using the timed "auto-ventilation" feature would help? Say have it on for 30 or 45 mins at about 1 or 2 pm when the sun and heat is at its highest so the cabin is warm and the moisture fully vaporized and then get the auto-ventilation system to evacuate it. I haven't been using the car as much over the last couple of really wet months so maybe a good 2 or 3 hour blast out at the weekend will dry it all out.

Matty - Just out of curiosity, how did you 100% determine that the screen seal wasn't leaking?
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Old 10th February 2016, 04:49 PM
mattylondon mattylondon is offline
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Quote:
Originally Posted by Lee S View Post
Matty - Just out of curiosity, how did you 100% determine that the screen seal wasn't leaking?
Maybe not 100% sure, but as sure as I can be just by visual checks outside and inside when I've have the interior trims off. Plus I try to avoid pressure washing sensitive areas like the seals and PDC sensors.
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  #15  
Old 10th February 2016, 05:23 PM
1781cc 1781cc is offline
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Guys, I am not sure if you had the same, but to see this looks like there is a leak, water is pooling and condensation is forming near the pool. It doesn't go, ever, aircon on, windows down, rear element on, nothing.

Also, looking at the inside, it appears to have discoloured the alcantara

Look familiar or defo a leak?

Tomorrow is when the glass guys are coming, so its an expensive exercise for nothing if its just ambient condensation, but I personally don't think it is - would like to be proven otherwise without having the expense of all the electrics under the rear seat failing first...

This only happens on one side only:





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  #16  
Old 10th February 2016, 05:29 PM
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Delboy Delboy is offline
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That's what mine looked like when the screen was leaking, it runs down the pillar and soaks the parcel shelf, if you strip out all the interior trim(not a bad job) you can then see where the water is coming in, and possibly try to resell from inside???
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Old 10th February 2016, 05:53 PM
Lee S Lee S is offline
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Mine is 10x worse than that. It's in the same place but goes across to about the start of the rear brake light and is where the small gap is. ie, there is none on the window above the parcel shelf but lots between the parcel shelf and glass, exactly like in the photo. I have the light platinum parcel shelf and there is no discolouration or staining or any swelling or ANYTHING to indicate a leak. Just the condensation. It is all very odd. I wonder if a damn good blast around the area with a pressure washer would show up some leaking?

I noticed last night that the rear screen was misted and i put on the demisters and it seemed to be on the inside. I put it down to cold weather outside and lots of moisture/breath/sweat etc on the inside. Still doesn't explain why its in that corner only though. What are the chances of ALL D3s having a poor seal in exactly the same place? But the evidence is borne out by those who have had the screen resealed or replaced and never had the issue again. Weird.
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  #18  
Old 10th February 2016, 06:04 PM
1781cc 1781cc is offline
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oh dear... I know you guys probably think I am being a bit weird here, but I would rather just get the glass guys to do and not mess around with stripping the interior out. Typically I would feel comfortable doing that, but I am currently dealing with the mother of all water leaks on my Cabriolet due to a failed seal on the scuttle panel and its allowing water (of which we have been having loads off) into the pollen filter, then down into heater matrix and out onto the passenger side footwell.

Last week I opened the car up to find 2 inches of standing water in there, so I have to gut the whole interior, including the dashboard to get the carpet out so I can dry it. Onto of that, I have to then reseal and test the scuttle/pollen filter so I think I have had enough stripping out cars as this is where I am currently at:





The S8 was meant to be my stock, no fiddling, pay and use comfortably car...

I won't even go into details regarding my "pastime" of which I still have stuff to strip out...





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  #19  
Old 10th February 2016, 06:11 PM
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Delboy Delboy is offline
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A seasoned pro then, it will only take you a little while
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  #20  
Old 10th February 2016, 06:19 PM
1781cc 1781cc is offline
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Quote:
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A seasoned pro then, it will only take you a little while
See last pic for having had enough and throwing my tools on the floor in despair!
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