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It seems as though my biggest nightmare with these old cars is the electrical systems.
I actually always carry a fire extinguisher in my car after one of my friends lost his car to an electrical fire.

I really need somebody with strong electrical knowledge to point me in the right direction.
I had to move my 66 Chevelle today to get at a ladder in my garage. the car had not been started in about two months and it was cold today around 33 degrees above.
The hood was open so I pushed it down just enough to see over it when moving the car. I turned it over a few times (very short intervals) it did not fire right away.
I noticed some smoke coming out from under the hood in the right front where the battery is. I got out immediately to check things out. The ground wire that goes to the core support from the negative cable got so hot it burned the coating off of the wire, and it melted the plastic on the top of my battery where it had layed on the battery.
What would have caused this??
The wiring on the car was replaced with new wiring harness when the car was restored.
I have replaced many voltage regulators and the alternator. the system has cooked one battery. something is wrong but what???? :mad:
 

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Sounds like the main negative cable going from battery to head or alternator bracket may be at fault. While trying to start all the current was going through the small ground, it can't handle that much current. I assume this all happened while cranking it over. Make sure the cable is good, not cracked, and solid connection to engine.
 

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"Finally" is absolutely correct. The small ground wire was the path of least resistance (not to mention the ONLY path) back to the battery. This brings a couple of points into question, not the least of which is what kind/year car we're discussing? (Your member profile doesn't say probably cuz you are not a member, hint).

-Why wasn't there continuity between the engine block, ground cable, and the negative post on the battery?!?! If you are having electrical problems, this is probably one of the main causes. Don't assume that because the cable is bolted to the head and the battery cable, everything is good. Obviously, there is a disconnect or problem with your connections here. Bad grounds are hard to detect (although, not this one this time) and cause many intermittent problems. For example, we recently installed a crate engine in a truck and it wouldn't turn over when we hit the key. Seems the new paint on the block of the new engine was actually insulating the ground cable end from the metal even though the cable end was bolted thru into the block! We ended up wire brushing the paint off the block in that area, wire brushing the cable end, and re bolting the ground cable back onto the engine. That solved the ground problem. I recommend you replace the GROUND CABLE entirely. This may be a significant cause of your previous problems.

-How many ground straps do you have between the engine and surrounding sheet metal and the frame? At least 3 or 4 are mandatory. Either buy a ground strap kit or make up the straps with 10 gage wire and soldered ends. I don't know if you are running an MSD box but they are notorious for missing at high RPMs if they are not grounded directly from the box to the block. That's an example of how critical good grounds are. After all, the ground is the other half of every electrical circuit in the car. You've replaced half of each circuit with new harnesses. Have you replaced the other and cheapest half, the ground cables?? At lease clean all the ground connections.

Above all, NEVER underestimate the importance of good solid CLEAN connections, especially ground connections. When in doubt, redo the connection. Soldered connections are superior to crimps. Always solder wire ends and splices (with electrical solder, NEVER acid core) wherever and whenever possible. A properly soldered connection will never come loose or corrode between the wire and the wire end, thus causing an intermittent connection at best, and a fire at worst.

Sounds to me (don't mean to be too presumptionus) that you have over looked the "ground half" of your wiring.
 

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Oh yeah, don't forget the rest of the grounds, I.E. from the gas tank sending unit to the frame. Is that clean and solid??? (probably best not to solder that wire end unless you are a Pro!!)

The frame is a good ground conductor only if the ground connections to it are clean, solid and free of rust.
 

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(I know better to mention this again. Always gets me in trouble.)
Engine ground straps have no purpose except noise shielding. Saying that, it is possible to have problems with 1970 and earlier Chevelle with the turn signals or running lights. That's because they rely on frame for ground. A single strap to the frame can correct that. 71 and later don't require a frame ground.
Fuel sender ground ties to the body not the frame.
 

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Originally posted by John_Muha:
(I know better to mention this again. Always gets me in trouble.)
Engine ground straps have no purpose except noise shielding. Saying that, it is possible to have problems with 1970 and earlier Chevelle with the turn signals or running lights. That's because they rely on frame for ground. A single strap to the frame can correct that. 71 and later don't require a frame ground.
Fuel sender ground ties to the body not the frame.
For a ’70 3 braided ground straps, 4 if it has an FM radio. FM radios were more susceptible to electrical noise. Do not make them out of 10 gauge, these straps are not supposed to carry any current, the fine braided wire is better for noise suppression. That big black cable going from the engine to the battery should carry the current. If you don’t have these straps installed wait until you have everything working correctly before replacing them, they can mask a real problem. I don’t have a functional radio at the moment and run without those straps. I’ll probably add them this winter so it will look nice but until I get a radio that’s all they’ll do for me. Having said that I agree with everything else Herb said. Bad grounds can cause just about every symptom under the sun.
 

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Must have been making a good connection at the Neg. battery post end but not on the engine end of the cable. Could be a bad cable or cable not making a good connection directly to the block.

Old late 70's Chevy pickups were bad about frying those little ground wires to the core supports.

I agree the ground straps don't have anything to do with the starter operation, you just need a good ground to the block (not to something else that's bolted to the block).

Years ago I worked at a Chevrolet dealer and the ground straps were installed on any new car that came in with a radio noise complaint.
 

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Guess my old days of RF engineering are still influencing me. Braided straps were forbidden in most RF environments for grounding, only solid or stranded insulated conductors were permitted. If the individual conductors of the braided ground strap seperate or become frayed, they can actually set up an RF field. But then, I wasn't dealing with car radio reception. Go with the experienced advice but make sure the connections are clean and solid, whatever you do.
 

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Originally posted by Herb:
Guess my old days of RF engineering are still influencing me. Braided straps were forbidden in most RF environments for grounding, only solid or stranded insulated conductors were permitted. If the individual conductors of the braided ground strap seperate or become frayed, they can actually set up an RF field. But then, I wasn't dealing with car radio reception. Go with the experienced advice but make sure the connections are clean and solid, whatever you do.
You may be right Herb, I don't know the whole theory on the braided wires. I know the computers I use to work on used either fine stranded wire or braided wire for grounding straps. Of course the 'best' method of inter-connecting frame grounds changed on a routine basis. I had lots of fun trying to eliminate electrical noise but it wasn't my area of expertise. In any case regardless of the type of wire we agree those ground straps are for RF noise and should not carry current. I'm sure if he follows your other suggestions he'll fix his problem.
 

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Discussion Starter #11
Thanks guys for all your insight to the issues with my electrical gremlins.
Sorry i could not get back sooner to give you more information about my car.
The car is a 1966 Chevelle SS convertible.
the car has been frame off restored a few years back.
all new wiring harness. all stock.
I will look into the condition of my cables and grounds.
 
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