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Old 04-14-2011, 12:27 AM
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Generator light stays on, 1968 Cadillac Sedan DeVille

The generator warning light stays on in my 1968 Cadillac Sedan DeVille. Key in or out of the ignition, it stays on. The only way to stop it is to unhook the battery. If I put the key in and turn it to on, the generator light goes off and the oil light comes on. Oil level is fine, though it could use a change. Also with the battery just hooked up the temp gauge(really more of an idiot gauge than a true one) is at a quarter. Turning the key pegs it along with turning the oil light on. Also pegging the temp gauge is the power seat switch. I have made no electrical mods, other than a small jumper on the neutral safety switch so I can get the ignition switch to work. The neutral safety switch is messed up. But I think that is another issue. There are lots of electrical gremlins in this car, so I don't want to try to take on too many at once.

I know there is a short, but where do I begin looking? I have the factory manual with all the wiring diagrams, but I don't know where to begin.

Also related, is it worth it to replace the generator with an alternator? I am not concerned about originality, just making the car a better driver. I don't want to mess with the pulleys if I can avoid it. If the change requires that it is probably not in cards anytime soon.

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Old 04-14-2011, 02:12 PM
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Well one problem is solved, the oil light is supposed to come on according to the manual. I still don't know why the generator light is getting power. I haven't found that diagram yet to know where to look. On the water temp gauge I need to find the under dash ground and clean it up. I don't know if that will solve the whole problem or just part of it. Maybe tonight I will get a chance to look up there and see what I can do.
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Old 04-14-2011, 05:05 PM
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Could be a defective voltage regulator
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Old 04-15-2011, 03:37 PM
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Thanks. I can check that out.
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Old 04-15-2011, 08:59 PM
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Looked at a wire diag. Looks like reg. most likely.
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Old 04-16-2011, 04:59 AM
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Might think about putting in an internal volt reg, best swap I heve done to mine, very easy to do, fixed alot of my gremlins.
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Old 04-19-2011, 10:30 PM
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According to the test(found it in the book finally) I just did the generator has a shorted diode. I unplug the wire from the generator and the light goes out. But get this, the water temp gauge again pegs out. And for some reason now(if I have the battery hooked up) it is always at roughly 1/4. When I hook up this plug I can hear I think it is the starter solenoid clicking.
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Old 04-21-2011, 01:20 AM
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Also, looking at it isn't the generator really an alternator? The factory service manual calls it a generator but looking stuff up online and just looking at it in person it looks like a alternator. I could replace the diodes pretty cheap, but I am thinking of just getting a more powerful one. Factory output is only 42 amps. I have found a 94 amp one at a price on either autozone or napa of about 60 dollars plus core charge. It just depends on my budget.

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Might think about putting in an internal volt reg, best swap I heve done to mine, very easy to do, fixed alot of my gremlins.
Probably going to do that. Thanks for the diagram, it should help.
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Old 04-21-2011, 03:56 AM
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Diagram was Doc's...... It was very easy to do.....I put in a 100 amp unit works very well, make sure you either replace the wire from the battery lug to the ext volt reg with a 8 guage wire or run an second 10 guage wire, I didn't and the old wire got pretty hot when everything was turned on.... ran a 2nd 10 guage from the batt to the radiator support junction then across to the horn relay and a seperate 10 guage from the alt battery lug to the horn relay splice......probably overkill but it works well now
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Old 04-21-2011, 06:14 AM
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yes it is an alternator and should be able to turn it into an internally regulated 3 wire fairly easy
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Old 04-21-2011, 06:34 AM
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Quote:
Originally Posted by silentpoet
Also, looking at it isn't the generator really an alternator? The factory service manual calls it a generator but looking stuff up online and just looking at it in person it looks like a alternator. I could replace the diodes pretty cheap, but I am thinking of just getting a more powerful one. Factory output is only 42 amps. I have found a 94 amp one at a price on either autozone or napa of about 60 dollars plus core charge. It just depends on my budget.



Probably going to do that. Thanks for the diagram, it should help.
A lot of teh manuals even today call them generators, never understood that
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