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Weird Electrical Problem!!


autonut
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Went to start a 1971 Buick Riviera that hasn't been running for a long time. Cranked over the engine to see if it would turn over okay and it did. But then I saw smoke coming from the right side of the engine compartment. The insulation was burning on the wire from the negative battery post wire to the chassis. There should normally not be any current flowing through this wire. Have never run across a problem such as this, which makes no sense. Do ANY OF YOU have any ideas?????

Lee

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I'm not sure how many people know this but....the electrons flow out of the negitive side of the battery, not positive. Your problem is what we refer to a IR drop. In other words you have a bad ground at the chassis or a high resistance connection at the negitive battery post. Clean both and you should be good to go.

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The insulation was burning on the wire from the negative battery post wire to the chassis. There should normally not be any current flowing through this wire. Have never run across a problem such as this, which makes no sense. Do ANY OF YOU have any ideas?????

Lee

Um, why do you think there should not be any current flowing in the negative wire? It's called an electrical CIRCUIT, meaning that there needs to be a closed circle. There's just as much current flowing in the positive cable as the negative one (and direction is irrelevant). Why do you think both cables to the battery are the same size?

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To Lee, original poster: I WILL GO AHEAD AND STATE WHAT IS ALREADY OBVIOUS FOR OUR INFORMED READERS.

The smaller guage ground wire from the neg battery terminal was never intended to carry the amperage load of the starter, it is a backup for accessories in case you lose ground from the engine block to the body. The auxilliary ground is a much smaller guage cable. The primary ground cable is bolted to the engine and then smaller ground straps go from engine to the body.

Check to be sure that the primary cable is bolted to the engine block or sturdy component on the engine, you have obviously lost that connection which is making the aux cable carry the starter load. If it is in place, clean it and the connection point,, it may just be loose. If the cable is green and swollen from acid contamination, REPLACE IT.

Edited by TexasJohn55 (see edit history)
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To clean this up a bit. The negative main cable from the battery should not go to the chassis, it should go to a clean bolt on the engine. The starter is the biggest current hog a car has so you need to rerun the cable to an engine bolt. I like to use one of the bolts on the bell housing. From there one should ground both the chassis and frame to the engine with a flat copper strap or a least a good size stranded copper wire. Do not use solid copper wire on cars.

As others have stated, there may be a problem in your cable that you can not see due to the insulation. I would consider replacing it as it's been smoked already.

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To clean this up a bit. The negative main cable from the battery should not go to the chassis, it should go to a clean bolt on the engine. The starter is the biggest current hog a car has so you need to rerun the cable to an engine bolt. I like to use one of the bolts on the bell housing. From there one should ground both the chassis and frame to the engine with a flat copper strap or a least a good size stranded copper wire. Do not use solid copper wire on cars.

As others have stated, there may be a problem in your cable that you can not see due to the insulation. I would consider replacing it as it's been smoked already.

Re-read my last post above: The negative cable obviously has an extra ground wire incorporated which is supposed to be grounded to the body. If the primary was bolted to the body panel it would still not "smoke" due to excessive current, only the smaller auxilliary ground could do that when the primary ground is not connected or functional. As for the insulation getting hot or burning, who cares, it is a ground cable.

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