The defrogger in the RS hasn't worked since I had it, the grid itself is intact AFAIK, The switch lights up when I turn it on, but it just won't heat up, is there a relay in the circuit? Where is it?

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Shane McConnell
macgyver@nethirdgen.org [*]Webmaster of www.NEThirdgen.org[*]1991 RS 305 T5 15.6@88[*]1979 Z28 ZZ4/2004R (In the future.)
I'm the kinda guy you bring home to Mother.

 

Sorry I don't have an answer for you Mac, but...

I have a wierd problem with mine too that might be relay oriented. I push the button, it goes on for one second, my lights go dim, engine looses power, I hear a springy boink type noise, and then the light goes off. One time it actually made the engine quit!

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88 firebird formula
350 Vortec TBI
214int/224exh, .471int/.491exh
Edelbrock headers
SIX-speed
Eats LS1's with a 2.73 open rear and 2 1/4 stock catback

My Formula

 

gah! what is it with these small things inside having such an effect on the engine? it was a bit chilly a few days ago, so i reached down and flipped my heater -lever-? over to 'heat', and the engine died... what in the world? i probably dont understand what is going on bc electricity remains a mystery to me, and always will be, but what gives?

 

I'm assuming that your '91 would be the same as my '92, so I looked it up in my Helm shop manual. The rear window defogger switch has a solid state electronic timer relay in the switch itself. There are no other relays in the circuit, so it may be that the switch assembly itself (i.e. the relay) has gone bad. As far as I could tell, the "on" light on the switch illuminates when you turn the switch on, not only if the defogger is actually functioning or not. Power is fed to the defogger grid on the left side and is grounded on the right. Make sure the grid is connected to the hatch struts on each side, and that the struts are connected on the other end. Other than that, check the "GAGES" fuse and the "PWR ACC" circuit breaker.

 

I went through this same kind of fun with the defogger in my GTA. It stays on for maybe 3 minutes and then shuts off. There is a relay in the dash on the passenger side right up front behind one of the covers. I replaced it...no luck. I then traced it down to the circuit breaker in the fuse box overheating and kicking off. I know this because I temporarily ran an external wire (HEAVY wire; these things draw 25-30 amps of current) and circuit breaker to the input side of the relay, replacing the original circuit. The defogger then worked fine. So...now I just need figure out where the short is. There isn't much else wired to that breaker (just the power seats and a couple of other things).