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Alternator Question

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15 comments

  • gunnut505
    In the old days, after installing an alternator or maybe it was a generator; you had to short it momentarily to set the polarity or something.
    That was before computers in cars though.
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  • grdad45
    A loose connection will heat up, especially on a DC system.
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  • dcon12
    quote:Originally posted by armilite

    My question is what could have caused that stud and wire to basically melt. Was it an internal alternator problem or could it have been heat related ????



    Heat. Don
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  • Ricci Wright
    Yep if it was loose it could have built up resistance and melted.
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  • sharpshooter039
    One of my work van kept dying going down the road, You could quickly turn the key off and then back on and it would restart. 2 different auto shops could not figure it out,, I was researching online and found other examples,, everyone of them said bad Alternator, It seams autozone alternators with the internal regulator had a habit of overheating , when the voltage regulator got hot it shut down the electronics and switching the key reset it. I drove it until it died,, immediately checked,, the alternator was so hot it was red,, shops could not find it because they never run it long enough to get that hot,, anyway autozone replaced it and it never died again
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  • Knifecollector
    Yes, it was melted due to heat caused by either a high resistance connection or loose arcing connection.
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  • Ditch-Runner
    sounds like a loose connection overheated
    the rubber boot I would guess could be easy found at a wrecking yard
    just a passing thought in the past I have improvised using a old a 90 degree spark plug boot .
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  • armilite
    quote:Originally posted by Ditch-Runner
    sounds like a loose connection overheated
    the rubber boot I would guess could be easy found at a wrecking yard
    just a passing thought in the past I have improvised using a old a 90 degree spark plug boot .



    I was thinking along those lines as well but was thinking more of a coil boot.
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  • Heavy Chevy
    1 more vote for loose connection.
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  • Heavy Chevy
    1 more vote for loose connection.
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  • Okie743
    Yep bad connection. Could have even been a bad weak crimp in the barrel of the connector itself.

    You better make sure your new crimp is good and crimped onto good clean stranded copper wire. Lots of the crimpers that just mash a barreled connector are worthless when used on crimp connectors that needs a real good long term high amperage connection. I've seen several of these type mashed connections fail.
    A star washer would also be a good thing between the connector and the stud nut. Some of those alternator stud nuts have a built in start washer so as to get a good bite on the ring terminal.

    If you made a weak crimp or crimped onto old blue glazed copper wire it will do the same thing again soon.

    AND when fooling around with that Alternator wire you better disconnect the battery. That wire has full battery voltage to that lug and if you get it shorted it's sadness, some of those vec alternator wires are not fused and some go thru a big (about 250 amp) bolt in fuse usually located under the cover of a under hood fuse box.

    Your old alternator is most likely still ok.
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  • grumpygy
    Could be like I just found on the HD. The New Battery died. Put a charger on it and it would not charge. I thought it was the plug in that was bad so Popped the seat. Went to pull off the ground wire and it was lose but the bolt was tight.

    Bolt was too long and did not tighten the wire. One washer was all it needed. And the battery was not dead just adding the washer and she fired right up.

    So when they built that alt they could have stud sticking out to far and the nut bottomed out before tightening the wire. The resistance would have been very great and fried it all.

    So I learned and old lesson. Double check that the connection is tight wiggle the wires.
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  • armilite
    quote:Originally posted by Okie743
    Yep bad connection. Could have even been a bad weak crimp in the barrel of the connector itself.

    You better make sure your new crimp is good and crimped onto good clean stranded copper wire. Lots of the crimpers that just mash a barreled connector are worthless when used on crimp connectors that needs a real good long term high amperage connection. I've seen several of these type mashed connections fail.
    A star washer would also be a good thing between the connector and the stud nut. Some of those alternator stud nuts have a built in start washer so as to get a good bite on the ring terminal.

    If you made a weak crimp or crimped onto old blue glazed copper wire it will do the same thing again soon.

    AND when fooling around with that Alternator wire you better disconnect the battery. That wire has full battery voltage to that lug and if you get it shorted it's sadness, some of those vec alternator wires are not fused and some go thru a big (about 250 amp) bolt in fuse usually located under the cover of a under hood fuse box.

    Your old alternator is most likely still ok.


    Probably not the stud and everything else in the immediate are on the old alternator disintegrated.
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  • Okie743
    WoW, Burned the stud off also.

    I've seen some alternators get close to doing that and it was actually caused from inside the alternator itself.

    The little locknut that holds the stud pressure connection SECURE inside the alternator gets loose (due to not being properly tightened by the person assembling the alternator) and the rear head of the stud starts making loose electrical connection internally, heating, and the heat ruins things in two directions, inside the alternator and outside the alternator and melting the insulators around the stud.

    I found this when repairing alternators before the heat got so bad that it ruined/melted all and I could see what actually started the bad heat connection due to the blue metal.[;)]

    Varies by the size of the alternator amps but these rear stud alternator connections are carrying from 35-70 amps at times for a few minutes on cars and pickups.

    Some of the older model Fords and GM's used a fuse link in this wire, molded into the alternator output wire. Some GM had the fuse link down at the starter stud, not user friendly to get to.[B)]
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  • pip5255
    loose connection was arcing causing heat, heat and arcing burned it up.
    replace everything with factory parts and use dielectric grease. I even use locknut when I can.
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