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Fried an alternator.. why??


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#1 Marker1989

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Posted 01 November 2010 - 12:14 PM

So I was on my way home the other night and noticed the voltage gauge was pretty low, so I turned off the radio and the heat and it went back up to normal in a few minutes.   Then about a mile or 2 from my house it started dropping again, this time it got to the bottom of the gauge by the time I got home.   I opened the hood and found the power wire to the alternator and its rubber boot to be extremely corroded, so I began taking the alternator off to go have it tested and while I was doing that the power wire just falls off!!   Does this sound like corrosion over time or a fried electrical connection?   After getting the alternator off I went to take off the first nut that holds on that power wire and it came off with part of the stud in it, and the same happened with the bottom nut.   So I have a nonexistent power wire stud, can that be replaced or do I need a whole new alternator?   I know I need to find out why this happened so I dont fry another alternator and wire right after I put it on..   So what would cause this and where do I start looking??
Thanks, Mark
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#2 Indiana

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Posted 01 November 2010 - 06:43 PM

battery acid maybe or just salt and rust.  That stud is put in from the inside and I think its part of the regulator or rectifier and its welded or solder to that part.  Just get it rebuilt.

#3 Marker1989

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Posted 03 November 2010 - 12:11 PM

I forgot about that option, I will probably do that.   The power wire was definitely melted though..  so thats kind of concerning to me.
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#4 mstieg

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Posted 03 November 2010 - 10:27 PM

The wire could have just been crappy and corroded.  That one handles more amps than any other wire (except prob. the starter on a cold crank), so no doubt it'll get warm if not conducting as it should any more after 2_ years.  My alt was bad (again) after maybe 3 years and little use, and I later found the wiring to be crappy inside the harness sheath after having already replaced the fried alt clip before.  Surely that had something to do with my other elec. probs.  No reason not to run a new alt wire really.  Don't even have to kill the old one, just piggyback it in parallel with a new 8gauger up to the fusible link box and the current will take the path of least resistance (the new one).

Ol' homeboy ProfessorQuest has a somewhat decent how to of this if you don't mind his 'tude and occasional redundancies.
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Edited by mstieg, 03 November 2010 - 10:28 PM.

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#5 Marker1989

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Posted 14 November 2010 - 07:42 PM

Well I soldered a new wire on and put a reman unit on the car and its been fine for about a week.   Im not sure what caused it but Im not gonna worry about it unless it happens again.
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#6 Tim_C.

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Posted 19 November 2010 - 02:13 AM

I would check the engine ground and body ground connections on the negative battery cable. Clean both of those. If they are corroded, then it could cause the alternator to think the battery is not charged, and it will full field itself and burn up.

If your old alternator was the OEM one, then I hope you didn't trade it in. A good rule to follow is to never put a store bought reman on one of these cars. What you get is very substandard parts inside compared to OEM, and a unit that won't last very long. Even a lifetime warranty isn't worth it when you keep changing junk.

You should always take your OEM alternator to a rebuilder who can rebuild with superior parts inside. You might pay a little more for less of a warranty, but you won't need one and you get a professionally rebuilt and assembled unit with better parts. The store bought units are usually slapped together by a $5 per hour or less foreign factory worker who has no clue about workmanship, how to identify problem parts, etc.. If they run out of heatsink compound, they assemble it anyway, and other similar things that we find all the time only in storebought units.
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#7 DzNutz

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Posted 19 November 2010 - 09:15 AM

Like Tim said, definantly check and clean the engine and body grounds on the ground cable. Also be sure to use a new wire from the alt to the batt. A corroded wire will creat so much resistance the alt will burn up.  Also if the batt has a dead cell the alt will constantly be trying to get it above 12v and burn up.




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