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Discussion Starter #1
I have a friend with a 91 GMC 4x4 V6. His alternator is not charging the battery. Here are all of the symptoms I know and things I've tried.

All battery connections are tight and good, battery good, heavy gauge wires from alternator lug post to battery are good - even had a heavy jumper in place between - no help. Fusible links in these heavy gauge wires (that connect to the alternator lug post with a nut are good. Replaced alternator, car still does not charge. I was checking the voltage across the battery posts, alternator lug bolt and other areas with a digital meter, battery voltage with engine running only 12.1 volts.

All of his dash gauges do not work. The fuse that runs them blows - I thought this might have been a different problem. Now I'm not sure. His alternator does not have the hole in the back where you can ground the field wire to the alternator case to check alternator output.

My son has a 94 S-10. I took his 2 wire connector off the alternator of his truck and it would not charge with that connector removed. Now that obviously has something to do with the charging circuit - but I don't know where the wires go or what they do. I didn't think the gauges were the problem, so I skipped checking that stuff out first. I thought the guy might of messed something up there and that was a separate problem. Now I'm not sure.

I hope someone out there understands and can help please.

Thanks,

Tom
 

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A friend of mine had a Dodge Omni GLS, his alt wasn't working. turns out voltage regulation came from the engine cpu! he had to replace the computer. I don't know if G.M. does it this way, but it might be a lead. Ask the dealer.

Tom
You can do anything you want to......ONCE!
aka "my 66 coupe"
 

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Discussion Starter #3
Thanks for the reply. You may be onto something. You see I don't have a GM service book - I only have the Haynes books. But looking at my wife's book for her model, I see that the gauge circuit leads to the alternator, and they identified in her book those 2 wires as turn on input. Thus the alternator needs a signal to "turn on". I unfortunately have not determined what the purpose of it is, but obviously he has a short in the gauge wiring, and this is not allowing the proper signal at this wire to enable the alternator to "turn on".

I hate computer cars! Mustangs are much easier.

Thanks,

Tom
 
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