[A4] Fogging Windows...

Richard Hurt rnhurt at gmail.com
Tue Jan 15 08:54:33 PST 2008

Absolutely!  You have to use the A/C and outside air in order to remove
moisture from the air.  Cooling the air has the side effect of removing
moisture from it as well.  Ever notice water dripping out of the car next to
you at the stop light in the summer?  That's the A/C doing it's job.  By the
same token it is necessary to have fresh (cold / dry) air coming in from the
outside.  As you respire you give off a lot of moisture (just breath on a
mirror) and if you just recycle that air the moisture won't go away.

In short, I don't think you have any leaks at all.  You would definitely
notice a heater core leak; the sickly sweet smell and film that sticks to
the inside of the windows is unmistakable.  In fact, my A4 will fog up quite
a bit in rainy weather if I don't turn the A/C on.  For a while I was like
you and tried to save fuel by turning off the compressor when I didn't need
it, but eventually I just set it on "Auto" and let it do it's thing.  It
makes the best decision most of the time.  I find it kind of ironic that I
have to re-heat the air coming out of the vents when I run the A/C in the
winter, but that's physics for you.  :)


On Jan 15, 2008 11:22 AM, Arthur Marks <aamarks at cox.net> wrote:

> As others have suggested there may be a problem that is causing the
> humidity
> (if there is a heater core leak I would imagine you'd notice the radiator
> fluid getting low). However, running it on Econ means the A/C isn't
> helping
> to pull out the moisture. It's a good idea to run the A/C at least once a
> month even in the winter to keep the system well lubricated. You might try
> starting out your trips with Econ off and then turning it on once the
> moisture is out.
> --Art
> ----- Original Message -----
> From: Derek Pulvino
> To: A4 Mailing List
> Sent: Monday, January 14, 2008 11:33 PM
> Subject: [A4] Fogging Windows...
> Only really notice the fogging occur when the weather gets cold (like
> down to 35-Fahrenheit or so), with any precipitation making it
> worse.  Most accumulation is on the edges of the windshield, tops of
> the front windows, and pretty much all of the rear windows.  I'm not
> aware of any leaks in the car, and I've got the climate control set
> to Auto, Econ off.  Didn't get any faults with the CC in running a scan.
> So, any ideas?
> dp
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