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Discussion Starter · #1 ·
Has anyone else had a problem with condensation forming on the outside bottom of the windshield when trying to defog the windshield. With my 2010 Outback I have this problem no matter how I adjust the hyvac controls - A/C -Heat - high fan- low fan, nothing seems to work and so I need to run the wipers
intermitantly to keep the lower half of the windshield clear. Had the dealer check it and they said everything is working properly. Have had the problem since new and I just cringe when ever conditions cause the windshield to fog up. Never had such a problem with 3 other Subi's and many many other cars. Anyone please if you can help.
 

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06 OBW 2.5, 05 Forester, had 03 H6 OBW
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AC is working really well and making the windshield cold. Turn up the temp or turn off the AC.
 

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2000 OBW, 2002 WRX wagon
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i have this problem when the defroster is on, no a/c.
The defroster turns on the A/C automatically. It is working well and it is not a problem.

It is because the bottom of your windshield is being cooled by the A/C (defrost setting) and condensation from outside is depositing on the window.

Trevor
 

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Discussion Starter · #6 ·
Beg to differ BHestor but it is a problem - can't see out the windshield- and if this is the way Subaru designed the defrost system to work they really made a third world kind of blunder. No way should clearing inside fogging purposely cause outside condensation so bad that you need to run the wipers. Never had another car do this from 1954 till now. I believe you are correct that it is a too cold A/C blowing on the windshield that causes this. However I think the Outback design/engineering in this area was poorly done to allow too much too cold air to blow on the windshield when defogging. With older cars I've manually used the A/C for faster defogging and not had any problem to this extent.

Maybe I just need to turn up the temp control to something closer to the outside air temp - will that assure a lower temp air stream to the windshield ?? Anyone know if this will mitigate the problem or is there another way to override the automatic turn on of the full blast A/C ? Thanks for all your imput.
 

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Discussion Starter · #7 ·
Hey CNY Dave - didn't mean to ingnor your advise - got carried away a bit. So if I'm not running the A/C it will automaticly turn on with the defroster and then I can maually turn it off or at least manually raise the temp ? Not great to have a two step proceedure to defog the windshield but better than running the wipers I guess
 

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06 OBW 2.5, 05 Forester, had 03 H6 OBW
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Yeah, as mentioned defrost automatically turns on the AC on most cars. On lots of days that is quite useful, other times not so much.

Just crank up the temp or turn off the AC and it'll stop.

On mine I can turn off the AC after selecting defrost, some cars maybe not.
 

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1999 obw 2.5l Auto 194,000 mi
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The condensation on the outside of the windshield is caused by the dew point. It is the relationship between temperature and relitive humidity. If the AC drops the temp of your windshield at or below the dew point humidity in the air will condense on that surface. The AC runs during defrost mode to dry out the air so it won't condense on the inside of the windshield during colder weather a much bigger problem than turning on the wipers. This chart shows those relationships
you can see that on high humidity days it does not take much to cause the condensing especially if your AC blows real cold. Simplest solution is to add a little heat to the air mix to raise the dew point on the glass.

 

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On the Benz I could turn off the AC, not sure that can be done on the Outback. I just raise the temp until it stops. I should note that I live in Fl and this happens a lot. Also on both my Hondas.
 

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As others have noted, when using either of the defrost settings, the AC is on. If the temperature setting is at the cold end of the range, it will only make the issue worse -- cold air will reduce the surface temperature of the glass, causing even more condensation. Whenever either defrost setting is used, the temperature should be turned up, so that the incoming air is first dehumidified by the AC, and then is warmed before being vented onto the windshield. This provides very dry, warm air, which is the fastest way to clear the window.

There is another way to remove condensation -- use the "floor" setting, rather than either of the defrost settings. In this position, there's still a fair amount of air going up to the windshield, and the AC does not come on. However, again, the temperature should be raised to warm the air. It's not as fast as the defrost settings, but I find it works quite adequately in many situations.
 

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Sorry to bring up an old thread, but I had a similar problem with my 01 outback and finally located and fixed the issue. Mornings following heavy rain I would find heavy condensation (sometimes an ice sheet!) on the windshield above the defroster vents and along the corners of the windshield. I verified that the AC tube was connected as pointed out in many posts on this site, which is was. I then pulled off the wiper arms and removed the cowl cover hoping to find it full of leaves and debris. Unfortunately, Subaru seems do have done a great job engineering this piece and there was very little to clean out. At this point I got the garden hose out and started spraying out the cowl area. I was spraying out all the nooks and crannies of the cowl/wiper motor area when I noticed that the cowl was not actually draining, and was instead filling up with water! The cowl is resigned to drain at both sides, running down between the front door hinges and inner fender. I removed the mudflaps, and folded the inner fender out of the way to find a hard pack of debris running from near the running board all the way up to near the top door hinge. I was shocked at the sheer volume of material that was removed! It has now been several weeks (and may rain storms) and I am happy to say that my once common occurrence of foggy windshields and extended defrosting periods is over. I am now ready for winter!
 
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