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Headscratcher electrical short

ngsd

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My gauge was only reading 11 volts and battery was dying so I started in the common place to look. It started and ran fine but lacking charging. When I looked at he battery lead, it looked like something shorted across the positive aux line. I am going to chalk it up as that but cant figure out for the life of me what would have done it. It is a 4G, painless harness explorer set up. The terminal goes to a megafuse before the battery and no other wire shoed any sort of burn and the fuse was fine. Is there anything I could have missed?
 

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DirtDonk

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Looks like phaser damage from an attacking Klingon bird of prey!:eek:
Is the big cable with the newly C-shaped ex-ring terminal from your alternator/mega-fuse setup? Was it always open like that, or did it melt in the carnage?

And just as important, have you fixed it yet and found the battery charges just fine again? Does not look like it should have impeded the charge, but it depends on what else may have taken a hit. Hopefully nothing...

Is the interface between the alternator and engine clean and free of rust/paint/powder coating? Do you have a dedicated ground between the alternator and engine and/or body?

Paul
 
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ngsd

ngsd

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Looks like phaser damage from an attacking Klingon bird of prey!:eek:
Is the big cable with the newly C-shaped ex-ring terminal from your alternator/mega-fuse setup? Was it always open like that, or did it melt in the carnage?

And just as important, have you fixed it yet and found the battery charges just fine again? Does not look like it should have impeded the charge, but it depends on what else may have taken a hit. Hopefully nothing...

Is the interface between the alternator and engine clean and free of rust/paint/powder coating? Do you have a dedicated ground between the alternator and engine and/or body?

Paul
Looks like phaser damage from an attacking Klingon bird of prey!:eek:
Is the big cable with the newly C-shaped ex-ring terminal from your alternator/mega-fuse setup? Was it always open like that, or did it melt in the carnage?

A: Yes from the mega fuse. All of the cables were new and the carnage caused the meltdown of the cable end.

And just as important, have you fixed it yet and found the battery charges just fine again? Does not look like it should have impeded the charge, but it depends on what else may have taken a hit. Hopefully nothing...

A: Yes, i put a new end on it and hooked it back up. Everything seems to be fine and it is charging at about 14.4v

Is the interface between the alternator and engine clean and free of rust/paint/powder coating? Do you have a dedicated ground between the alternator and engine and/or body?

A: The engine is grounded and there is no dirt or powder coating. Everything was new.

That is why it is a headscratcher. If I had to guess judging but the shape of the burn, it looks like something like a screwdriver took a direct ground to the positive terminal and caused the heat but if it happened while sitting or driving I would have no idea what that would have been. If it happened while working on it I surely would have known that explosion. Nothing on the hood to come down and it is fiberglass, the wildhorses battery box is steel and very close to it but that area on top of it would not of touched anything. If not a grounding issue I hope it doesn't happen again as I would fear a fire issue with that much heat. I would think if it were an engine ground issue it would have hit the cables/fuse first not the top of the terminal.
 

DirtDonk

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I agree it looks like something touched it. I wonder if someone was messing around under your hood?
I also agree that other problems would’ve blown the fuse first. And even if not, instead of a damaged area across the whole connector and wires, you’d have seen outer jacket damage to the main cable from overheating.
Mystery for sure…

Do you have a 150, or a 175 fuse?
Don’t think it matters in this case. I was just curious.
 

armynavy17

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It's hard to tell, but it almost looks like there's some discoloration on the battery hold down in the first picture.

Was it parked somewhere where it could have been messed with? Definitely looks like a screwdriver or wrench grounding out, maybe someone was hoping to score a free battery.
 
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ngsd

ngsd

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Unfortunately I don't drive it enough to leave it parked anywhere that somone could have messed with it. The hold down can't touch it but something may have arc'd across it. The fuse was a 175. I just changed to a 125 to be safer.
 

DirtDonk

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Not sure that’s really safer. Your cables are still being well protected by 175. Takes a lot more than that to melt a 6, or 4 gauge cable.
A 125 is below the threshold of what the alternator can put out for an extended period of time. A 3g can sometimes output as much as 150a.
Not that it happens very often, but you wouldn’t want the alternator to blow the fuse just from doing its job.

You can keep the 125 if you want, but make sure to carry that old one as a spare in the glove box just in case.
 
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ngsd

ngsd

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Good advice, I think i was hoping that it blew first if there was another issue. I think I will keep an eye on it for a short time and if no issues I will put it back the way it was and chalk it up to a errant part landing on the terminal.
 

Rustytruck

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seeing no obvious cause and the battery case melted something got very hot.likely a loose connection. a ground short would have blown off the wire at the battery with so many available amps. I would also check the motor mounts in case torquing the motor uncontrolled would pull on the wire attached to the battery., looks like there was a battery wire pointing straight up. so. whats not working that may be missing a battery connection? Its an odd failure looking like someone trying to hot wire the truck or a rodent wearing steel cleats.
 

Oldtimer

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I say check your tool box.
There is probably a missing wrench or extension, that got left under hood.
Slid off fender, shorted battery, and landed on street.
 

Jdgephar

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Just FYI, The mega fuse only protects the wire from the alternator to your battery. The arcing you had is directly on the battery post positive to ground. A 125, 150, or 175 amp fuse won't matter when a short is at the battery post. The current in that short is not going through that fuse. If it was, your 175 amp would have opened, instead of the missing copper on your terminal.

You are still protected with the 175 amp fuse. As Paul mentioned, you are at risk that the alternator will blow the 125 amp fuse.

Sent from my SM-G981U using Tapatalk
 
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ngsd

ngsd

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Just FYI, The mega fuse only protects the wire from the alternator to your battery. The arcing you had is directly on the battery post positive to ground. A 125, 150, or 175 amp fuse won't matter when a short is at the battery post. The current in that short is not going through that fuse. If it was, your 175 amp would have opened, instead of the missing copper on your terminal.

You are still protected with the 175 amp fuse. As Paul mentioned, you are at risk that the alternator will blow the 125 amp fuse.

Sent from my SM-G981U using Tapatalk
Yes I think that is the concensus. There had to have been something shorting across it. I just can't imagine what it was. The 175 is already back on. Thanks
 

El Kabong

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