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Old 07-20-2015, 05:49 AM
apd628 apd628 is offline
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Default Killing Alternators

I have a 1981 that keeps eating alternators. The first time, I was driving along and the battery light came on. I checked the belt tension, battery connections, battery ground, and the fuseable links on the starter, and the starter ground all good.

I tested the alternator while running and it was putting out 12.3 volts or so. I checked all of my fuses and they were fine. I pulled the alternator, and it had a fried voltage regulator, and diodes. Got them fixed, installed it, and battery light still on.
I checked the alternator, still only putting out 12.3 volts at start up and it had another fried voltage regulator, but diodes still good.

The battery light dims as the RPM's go up, but it never goes out.

I am a little slow on the uptake, but I think the issue is somewhere on my wiring harness, and not the alternator.

Anybody have a clue what is killing my alternator?
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Old 07-20-2015, 12:05 PM
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mrvette mrvette is offline
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The regulator plug has two connectors on it -- the replacement plugs we see in the shelves are typically red and white wires.....I dunno what GM wires are.....so pull the regulator plug, and with ignition off the MOST CLOCKWISE/RED wire should have 12 volts on it, the other one nothing....turn on the ignition and the other wire/white/LEAST clockwise, should have 12 on it, that is fed through the dash light saying bat/alt/whatever red warning light..... ground that wire and the light should light all the way.....

methinks someone replaced that regulator plug and got the wires backwards.....
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Old 07-20-2015, 08:58 PM
apd628 apd628 is offline
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Thanks for the reply mrvett.
I performed the check you outlined above. The most clockwise, the red wire in the plug, shows 12 volts with the switch off and the white wire, least clockwise shows 0 volts with the switch off.
Switch on, both of them show 12 volts.
Switch on, the two wire plug installed into the alternator, battery light on, switch off, battery light off.
Switch on, pull the plug, battery light goes off.

The alternator is a chrome, Powermaster 140 amp 3 wire, internal voltage regulator model.

Thanks again.
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Old 07-20-2015, 11:56 PM
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mrvette mrvette is offline
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Anyone did anything with the starter recently?? and on an '81 there may well be a white plug in the wiring harness going down to the starter region from up high on the firewall, look at that plug, that SOB has to be white and clean, any brown/black means it's burnt up......for some reason the later sharks had that plug in them, and I have seen them burn up, causing all sorts of problems..... AND in this starter thought, check that there is NOT a black wire about 10 gauge tied to the battery terminal on the solenoid.....that damn wire is a ground for the HVAC blower and the Wiper motor on most sharks, maybe even feed through that white connector, I changed the wiring to make connection on TOP of my engine.....

after that, I just dunno without being on site.....unless you maybe have further info.....

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Old 07-21-2015, 03:31 AM
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The starter looks to be pretty old and untouched for awhile, but it works fine. Think I found the plug, took a photo of it, tried to attach it, but it is in my photos. It is definitely not lily white, it is on the firewall and the bottom half of the plug wires, disappear down to the starter area. The ac blower motor ground appears to have been relocated to one of the high pressure lines coming out of the ac dryer.
Reference my post concerning that, it appears the ground was not connected to the blower motor, pot a ground on it and it works great. I will install a c4 blower motor on it, as the ac unit in the last was marginal at best.
Thanks again.
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Old 07-21-2015, 11:59 AM
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mrvette mrvette is offline
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That damn white plug was made by MOLEX corporation, and used to appear in TV sets back years ago, and talk about problems, they would not burn up, but the assy work stunk, and so connection problems up the ass......

now I see them in a high moisture position under the hood of a car....great, and of course the plastic turns brown because of all the heat generated via the wiring, I would pull it apart and see what is what on those wires, I bet one of them been super hot, and maybe even burnt/corroded the connections to open up and not work.....causing God knows what.....

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Old 07-21-2015, 10:24 PM
apd628 apd628 is offline
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The 49.00 rebuild job alternator that I picked up at the local parts store did the trick.
My six month old 350.00 chrome plated Powermaster alternator is the culprit, not my car.
Car running and charging fine now, what an education. I need to remember the most complex appearing problems are often solved by the simplest solution. A paraphrase from some German philosopher from centuries ago.

Thanks MrVette
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Old 07-22-2015, 10:21 PM
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Quote:
Originally Posted by apd628 View Post
The 49.00 rebuild job alternator that I picked up at the local parts store did the trick.
My six month old 350.00 chrome plated Powermaster alternator is the culprit, not my car.
Car running and charging fine now, what an education. I need to remember the most complex appearing problems are often solved by the simplest solution. A paraphrase from some German philosopher from centuries ago.

Thanks MrVette
Some times chrome is NOT faster.....TFF..... but do pay attention to the white wiring plug connector there, it's a trouble spot over the years.....
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