Alternator Ground Wire Melts
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500, 472, 425, 368 Discussion, Alternator Ground Wire Melts in Cadillac Engine Technical Discussion; Hey all. I've got my HEI distributor all hooked up, but car still won't start. Starter motor only cranks a ...
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    Brother_B's Avatar
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    Alternator Ground Wire Melts

    Hey all. I've got my HEI distributor all hooked up, but car still won't start. Starter motor only cranks a couple times before it struggles and gives up. The ground wire off the alternator keeps smoking and melting. I've replaced it several times. Now it's a 10 gage wire, grounded to the wheelhouse like the manual says.

    A friend took a look and said my battery ground wire was all wrong. It was grounded to the chassis. He said it needs to be grounded to the engine block, for example to an intake manifold bolt. I tried this, no help. My friend also says it could be the frame-block or body-block ground wires.

    Does my problem sound like a ground wire problem? And are there standard locations for these other ground wires? I read somewhere that it can help to just run a wire from neg battery post to frame, and then to body - Will this help if my problem is a bad ground? Thanks, B

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    The Ape Man's Avatar
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    Re: Alternator Ground Wire Melts

    Some of those beasts had a huge braided wire which ran from the starter motor bolt right to the chassis frame. If your heavy battery ground (negative) wire goes to the sheet metal instead of the block AND this braid is missing or loose then the alternator ground wire might be seeing full current draw from the starter. Not a happy situation. Look for the braid. If you cannot find it then you could relocate the heavy battery negative to the engine block.

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    Re: Alternator Ground Wire Melts

    Welp, I already relocated the negative cable to the block, no dice. Are you saying that could have fixed the problem even if that braided ground wire was loose/missing on the starter? Either way, I like your theory. The starter is one place I haven't checked. I haven't been able to look at the starter because the car's parked in the sand/dirt so it's hard to jack it up to get under it. Since it used to run fine with the battery neg grounded to sheet metal, I think something else has worked loose that I can't see from under the hood. Looks like I'll have to find a way to jack it up. I'm thinking plywood.

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    Re: Alternator Ground Wire Melts

    There are at least three braided grounding straps on this car. One goes from the starter to the block as described. Another is near the evaporater housing and goes fron body to block. A third is near the front right corner under the battery and connects frame to something (I can't remember - block ?) these all need to be clean and tight or you'll get the meltdown syndrome.

    What I don't remember is a ground wire on the alternator. I fried my original several years ago and got a chrome "single wire" alternator - only to find out that it was not putting out enough voltage below 2000 RPM. So during the rebuild I had my original regulator hollowed out and a small transistorized reglator installed inside it and the whole set-up works fine.

    But I still don't recall a ground wire from the alternator.

    These big block Cadillac motors, especially 1968 are notorious for amplifying small ground problems. I have some info at home from the Cadillac LaSalle Club - I'll be there next week and will try to find it. I recommend getting a shop manual. If you look and are patient you can get one very reasonable on ebay.

    Last thing, check both ends of both battery cables, VERY important. Every so often my battery ends get all oxidized and i have to clean them, this is more noticable on a hot engine. I've parked, ate lunch and had no nothing when i got back to the car. a quick clean of the terminal ends and good to go. I really should get new cables, but i like my black and red painted ends - maybe I'll get new cables anyway...

    last last thing:

    Get rid of that HEI and put back your original distributor and points / condenser My car flies on an essentially factory igintion system. I used to get it up to 95 with the top down on essentially 6 & 1/2 cylinders!

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    Re: Alternator Ground Wire Melts

    Mike:
    AAUGH! Don't tell me to get rid of the HEI! Too late for that! (I destroyed the points dist when I removed it. To go back to points now, I'd be hitting the junkyard.) I must say you are first fan of points I have seen on here! Nothing wrong with that!

    Thanks a bunch for info on the ground straps. I definitely need to get this thing off the ground so I can get under and look for the ground from starter to block and the end of the + wire from the battery.

    I know there's differences from '68 to '69, but I do have a manual, and it says very plainly that there is an alternator ground wire. It actually says "ground at wheelhouse". None of the other grounds on the wiring diagram say physically where they go, just the standard ground symbol. And I haven't found any mention of any ground wires anywhere else yet. For example, in the starter removal/assembly instructions, it says nothing about disconnecting or attaching one. But I hope you're right and there is an obvious loose ground strap off the starter, I'll hook it up, and this beast will roar to life!

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    Re: Alternator Ground Wire Melts

    Quote Originally Posted by Brother_B View Post
    Mike:
    AAUGH! Don't tell me to get rid of the HEI! Too late for that! (I destroyed the points dist when I removed it. To go back to points now, I'd be hitting the junkyard.) I must say you are first fan of points I have seen on here! Nothing wrong with that!

    Thanks a bunch for info on the ground straps. I definitely need to get this thing off the ground so I can get under and look for the ground from starter to block and the end of the + wire from the battery.

    I know there's differences from '68 to '69, but I do have a manual, and it says very plainly that there is an alternator ground wire. It actually says "ground at wheelhouse". None of the other grounds on the wiring diagram say physically where they go, just the standard ground symbol. And I haven't found any mention of any ground wires anywhere else yet. For example, in the starter removal/assembly instructions, it says nothing about disconnecting or attaching one. But I hope you're right and there is an obvious loose ground strap off the starter, I'll hook it up, and this beast will roar to life!

    Im staying with points in my 742 just for the fun of it.

    Keep use up to date ..

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    Re: Alternator Ground Wire Melts

    ERGH. Try retarding the timing by turning the distributor in the same direction as the ignition rotor rotates. Start with about 30 degrees or about 1/10 full turn. You might have a crapload of initial advance which can make the poor starter draw extra current. Always leave the air cleaner in place when working with this stuff as you could lose your eyebrows or worse. Consider getting a starter with 8 volt windings. They were the only thing easily available that would start my high compression 507 and I've been using them for over 20 years.
    A properly retrofitted H.E.I. will blow conventional points systems away.

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    Re: Alternator Ground Wire Melts

    Thanks to everyone that chimed in on my many questions. HEI distributor is now functioning, and it's even wired up correctly. I located 2 of the 3 ground straps that Mike mentioned. One was broken! Right on! After fixing that stuff, a friend finally came over and determined that my timing was out about 90 degrees. Whoops. Well, thirty minutes later he got it started for me. Put it to the test on the highway and scary bridge today. Now on to the million other things that need attention. Checked off so far: distributor, plugs/wires/ carborator, fuel pump, vaccum modulator, governor, battery, speedo cable... This weekend, fun stuff like the horn and radio. And a look at the exhaust and, oh yeah, replacing the ported vacuum switch. At least she's running finally!

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    Re: Alternator Ground Wire Melts

    How does she run now with the HEI, do you notice a huge diffrence? hows the power compaired to the old points?

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    Re: Alternator Ground Wire Melts

    Fords with 352s and 390s had similar starter/grounding problems when engines were hot.

    It seems that Caddy always had that problem back in the old days.

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    Re: Alternator Ground Wire Melts

    There IS a ground from the external regulator to the wheel well (maybe thay called it wheelhouse in the manual???) And the regulator is considered an integral part of the alternator (even thugh they're separate items). That is a llittle pigtail that needs to have a good contact and of course the grounding strap from the wheel well to the frame has to be there as well! At least it is not running. the third strap is up near the evaporator housing - only access is from under the car behind the starter.

    you can keep the HEI distributor, i was only razzing you. I'm also not racing my car and so don't need to ruin the appearance of the car with a bloated HEI ignition system. this car always starts right up and like i said it went 95 mph with the top down BEFORE the rebuild.

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