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Lead red wire to alternator hot

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Old 11-15-2007, 05:07 PM   #1
platergd
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Default Lead red wire to alternator hot

I have been trying to trouble shoot why the lead red wire on my 91 corvette alternator has been getting hot enough to melt the plastic wire harness around it. I have had the alternator checked and it was ok. I unpluged just about all of the fuses leaving just enough to keep the car running and it still gets hot. Could it be the voltage regulator in the alternator? My voltage regulator needle runs close to 18 volts even with the AC and lights on but has never gone in the red. Has anybody else had this problem? I can't figure this one out. Where does that red wire lead to?
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Old 11-15-2007, 06:10 PM   #2
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May be a starter problem?
That wire should go to a relay behind the battery.
Someone may have tied something into the wire pulling it to ground.
If it went to ground that would make the voltage go up and get the wire hot.
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Old 11-15-2007, 06:52 PM   #3
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Quote:
Originally Posted by platergd
My voltage regulator needle runs close to 18 volts even with the AC and lights on but has never gone in the red.
If 18 volts isn't in the red, it ought to be. I consider 15 volts to be marginally too high. BOTH red wires to the alternator are direct battery feeds through fusible links. One is the output generated by the alternator, and the other feeds the regulator. It does sound like a regulator problem. Unless there is a short in it, it isn't likely to be anything to do with the starter. And if it were starter related, it would have drained the battery before you tried to start it.

RACE ON!!!
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Old 11-15-2007, 09:48 PM   #4
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The reason why your red alternator wire gets so hot is because at 18 volts, your alternator is charging the battery near its maximum rated current, or about 130 amps. The voltage regulator in your alternator is DEFECTIVE !!!!!!!!!!!!!!!!! Either replace the voltage regulator, or replace the entire alternator! GM says maximum alternator voltage must not exceed 16 volts. And if my alternator put out 16 volts, I would replace the voltage regulator. Normal alternator output is 14.7 volts cold and this drops to 13.7 volts hot.
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Old 11-15-2007, 11:47 PM   #5
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Holy schmidt......18 volts is EXCESSIVE for a 12 volt system car. with the above two posts. I would question the compentance of the person who tested the alternator.
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Old 11-16-2007, 02:18 AM   #6
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Default Lead red wire to alternator hot

Thanks. One more thing if this is any help. The the red wire starts to get hot at the alternator lead first and radiates back down the wire"?". I unplugged all the fuses and turned on the headlights and instantly the wire got hot with no effect on the voltage meter which was close to 18 volts.
I'm going to buy a new alternator. It will be a costly mistake if it is something else. Comments if anyone has any.

Last edited by platergd; 11-16-2007 at 08:20 AM.
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Old 11-16-2007, 07:18 AM   #7
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If you want to be sure(everybody else already is). Put a meter on the wire at the alternator and measure the voltage there. If you don't have one, you can get one for less than $20.00. I have never seen anything more than 15 volts, mine runs at 14.5 MAX!
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Old 11-16-2007, 10:20 AM   #8
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Default Lead red wire to alternator hot

Well, back to the drawing board. I brought a new alterantor and the red wire is still getting hot. When I disconnect everything, The wire still get warn but not as fast as when I put all the fuses in. Could this be a major ground or something as simple as the stereo grounding out "?".
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Old 11-16-2007, 10:38 AM   #9
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For some reason you have a large current load on your electrical system and the alternator supplies current when the engine is running. One thing you should check is the condition of your battery. Everything off, measure the voltage across the battery terminals. At 12.0 volts or below, the battery is considered discharged and the alternator will supply large current to charge it up. If you have a shorted cell in the battery, it will measure 10 volts and the alternator then will charge with very large current causing a hot alternator wire. But, at 10 volts, you may not be able to crank the engine. Engine off, disconnect the negative cable on the battery and connect an ammeter (at least 20 amps full scale) from the neg cable to the neg post on the battery and see what the current is ignition off then ign to run.
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Old 11-17-2007, 01:04 AM   #10
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You appear to have a dead short in your wiring or a problem with the battery as described above. Carefully check the red wire to make sure it has not worn its insulation off and is touching part of the frame or engine. Also, examine the wires going to your starter for shorts or grouding to the frame of the car. You may have top open some of the plastic conduit to trace the red wire.
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Old 11-19-2007, 02:53 PM   #11
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Default Lead red wire to alternator hot

Thanks I'll be checking all those areas.
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