🚀 go-pugleaf

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

First remember that most defrosters are relay operated, that is
the fuse inside the car (in your case) *only* covers the switching
circuit.
> defective (there was a mysterious large metal-enclosed one that

The large metal box is a circuit breaker with an automatic reset.
They are usually  used for headlamps wipers, etc...
> works when I activate the defroster.  The connections at the
> 	Jeff Percival ...!uwvax!uwmacc!jwp

O.K. , here's some tips. Check under the hood, there is a 30 amp
fuse under there near the alternator (the power for the window is
drawn directly from the output post of the alt.), it will be a 2.5 inch
white (probably) snap together affair. The relay for the window
could also be bad, it's under the hood near the wiper motor.
I would almost bet that your problem is either a blown fuse, or
a melted connector in the same wire that carries the fuse under
the hood. I had a 79' Pontiac with similar problems.
gpw
-- 

George Wilkin AT&T Network Systems   usenet ihnp4!ihlpf!gpw
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> 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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> 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 (there was a mysterious large metal-enclosed one that
> defied visual inspection).  The dashboard indicator light still
> works when I activate the defroster.  The connections at the
> rear window appear to be intact.  Can anyone suggest further
> troubleshooting?  I'd sure appreciate it.

I had an 81 Malibu wagon with the same failure. That metal box is
a relay not a fuse. The defogger draws too much current to use an
ordinary switch, also the relay has a timer built in to attempt to 
keep the defogger from melting  itself. In mine the relay went bad
(~$30). Have you checked to see if power is getting to the defogger
with a voltmeter or light? If it's not, it would be my guess that it's
the relay. If it is, then I'd suspect the window grid itself is open. 

A WORD TO THE WISE: NEVER leave a GM defogger on any longer than
necessary. They have a really nasty habit of cooking themselves if
just turned on and left for the timer to shut them off.