Windscreen fog, a cure.

[colin cohen <102621.2256@CompuServe.COM>]

I think it was Tim G. who posted a problem with his demist on a new A4. He did
not tell us whether he had checked that there was warm or cool air as the case
may be coming from the screen outlets, but as that is a basic test, and we are
all so car savvy on this list, I will let it go at that.  But add this:

We have seen this type of problem on the plastic/acrylic bubbles of helicopters
in the aviation world, the problem is caused by a number of things:

1) There are oils in the plastic trim around the screen which condense on the
glass if the car/chopper is allowed to build high interior temps (100+F);

2) The glass gets cleaned by materials that are not completely clean,
depositing oils on the screen. Eg: a cloth that may look clean, but was washed
using some type of fabric softener.

3) Smokers can deposit a residue, as can pollution, and plastic extract oils
from the vent system ducts themselves after the fan is started up shortly after
sitting in 100+ temps.

The fix: 100% isopropyl rubbing alcohol on a alcohol dipped soft cotton or non
fluff cloth. Usually two applications are required, one to dissolve the oils
(thin them and reduce their adherance) and a second to remove.  There may be a
need for another application a week later. Thereafter wash the interior of the
screen with lightly wetted newspaper. Never use glass cleaner because it has a
wax in it.

Good luck wherever you are.