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From: pwv@fluke.UUCP (Pat Vilbrandt)
Newsgroups: net.auto.tech
Subject: Re: '81 Malibu rear window defroster...
Message-ID: <1018@vax2.fluke.UUCP>
Date: Tue, 19-Nov-85 11:56:18 EST
Article-I.D.: vax2.1018
Posted: Tue Nov 19 11:56:18 1985
Date-Received: Wed, 20-Nov-85 08:24:54 EST
References: <1703@uwmacc.UUCP>
Distribution: na
Organization: John Fluke Mfg. Co., Inc., Everett, WA
Lines: 37

> The rear-window defroster in my '81 Malibu has stopped working.
> I checked all the fuses in the fuse box, and none appear to be
> defective ...

>	Jeff Percival ...!uwvax!uwmacc!jwp

Assuming that all the fuses are intact and you have 12 Volts to the rear window
defroster, the problem could be the *window* itself.

The rear window defroster is a pattern of conductive ink that is screened onto
the glass.  This pattern works like a big resistor, heating up when current 
flows.  If the defroster is left on for an overly long time, it gets very hot
(inadvertently turning it on during hot summer months could do this also).
This causes the conductive ink to increase in resistance to the point where
not enough current can flow to heat the window.  I have seen this happen to 
many cars, more so when I was also going to school back there in Madison than
I have seen here in the Seattle area.  Must be the colder winters??

If this has happened to your defroster, you will probably have a few localized 
hot spots on the rear window where the resistance of the ink has raised, but
be careful!  The hot spots can be hot enough to burn skin (I speak from 
experience)!

Newer GM iron have a timer built into the rear window defroster switch to 
prevent this problem.

Good Luck!

-- 

   Pat Vilbrandt
   John Fluke Mfg. Co., Inc.
   Everett, Washington USA
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