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Re: Fog in the car.

To: <shop-talk@autox.team.net>
Subject: Re: Fog in the car.
From: "Tim Mullen" <Tim.Mullen@trw.com>
Date: Mon, 18 Dec 2000 07:44:13 -0800
"Rex Burkheimer" <rex@txol.net> wrote:
>
> That was my first thought, but if your core was leaking you would smell
> antifreeze, and apparently you do not.

Not necessarily...  Depends on the size of the leak.  We didn't smell
any antifreeze in my son's car, although the residue on the windshield
felt somewhat "oily".  And it was a "big" leak...

> Apparently the warm moist air from the heater is hitting the colder, drier
> air from the interior and condensing out into vapor.

Possibly.  That is what creates the "fog" on the inside - even without
a leak.  Actually, the moist (and possibly heated) outside (or inside) air 
contacting the colder windshield.  Cold air cannot "hold" as much moisture
as harm air, hence the condensation...

> The question is how the heater air becomes more moist than the
> interior.    Perhaps there is condensation left from the previous day,
> trapped in the ductwork. Have you checked the old drain tube from 

That tube was there to remove the condensation created by the A/C.  
Normal usage will not create condensation (at least no a noticeable amount)
in the air box.  The condensation is caused by the air being cooled by 
the A/C.

My bet is that the heater core is leaking.  Especially if you have removed 
the A/C.  You might have disturbed the heater core and caused a marginal
one to start leaking.  We did that in my son's El Camino when we changed
the heater hoses.  The windshield would fog up almost immediately.  The
replacement was rather easy. and done from the engine compartment (I 
suspect that the Impala is similar.  I was tedious, but only because I had 
to dig through the tar-like sealer to find all the little screws that held the 
"air box" together, then resealing afterwards.  The new heater core was 
only around $20.

Tim Mullen

Chantilly, VA

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