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Re: froster not defroster?

RODNEY MICHAELSON <HOTROD@pacbell.net> wrote:

	Can one of you help with a problem with my daughters '91 90?
	Here in the Northern California where the rain has come to live
	day in and day out my daughters '91 90 when she turns on the
	(it has automatic climate control) the front windshild will fog
	instantly and take a few minutes to clear up. I first noticed it
back in 
	September when I was on the freeway and hit the defrost button.
BAM, the 
	world vanished in a mist. It would happen every once in awhile
after that 
	but now it is everytime according to my 16 year old daughter.
	Any suggestions?

Condensation occurs when the dew point of the air blown upon the
windshield is higher than the temperature of the glass.  This can happen
if the air is very wet and radiational or other cooling has made the
windshield temperature lower than that of the air.  This is more likely
in NH than CA.  It is best to warm up the car heater before attempting
defrosting if this is likely.

You may have a very wet air conditioning plenum.  To investigate this
you need to examine water ingress and egress.  The plenum drains
moisture via a tube (Bentley calls it a valve) that exits the firewall
below the battery.  This tube can become blocked for various reasons.
To inspect it requires removing the panel below the glovebox, a plastic
panel support, and the computer on the firewall, then pulling the tube
from both the plenum and the firewall.  Reassemble in reverse with some
colorful language directed at team door handle.

Water may also be draining into the air circulation system via the air
intake below the windshield on the passenger side.  You will have to
dislodge the plastic tray that covers the passenger side windshield
wiper mechanism to investigate this.  You should also check to see that
the plastic trays are properly mounted, and that water can run off the
windshield and these trays properly without draining into the interior
air intake.  Look below the trays to see that the drains at the sides of
the car are clear, and that the air intake to the squirell-cage air
blower is well sealed and free of mouse nests.  Seal any suspicious

....  Kirby  (kirby.a.smith@lmco.com)
New Hampshire, USA
2 X 1988 90q