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Old 06-06-2020, 05:06 PM
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Default Any Electrical Guru's out there? Dead Short Issue...

I have an electrical issue with my 69 Z after just going through the entire car and freshening it up with a thorough cleaning. The car has its untouched original harness throughout and it just experienced a dead short while it was parked after a road test? There are no cuts or splices anywhere to be found and no broken wires that I can see going to ground. Whatever caused this dead short occurred right after it was parked from a short cruise just the other day. Ignition was turned off and the car sat there with me standing right in front of it when I heard a snap which was immediately followed by a high current meltdown.

It quickly fried the 20" fusible link between the + battery terminal and the + distribution block on the rad support. I immediately grabbed a wrench and pulled the ground then the positive cable and surveyed the damage which claimed the fusible link. The link was draped around the lower front corner of the battery and the link became so hot that it melted through the corner of the battery case which caused the battery to leak some acid into the tray as well. In hindsight, it now has me wondering if maybe the wire got pinched between the battery and the rad support but never thought to check that before I yanked the battery out due to it leaking and me rushing to get it out of there after the fact.

The only things recently changed on the car that could perhaps be suspect would be a restored 367 Starter with a new solenoid, or perhaps a used 837 Alternator in original unrestored condition. It was tested as charging before it was installed. Those are the only 2 items that I can point to that have live power going to them while the car is switched off, hence my curiosity if one of them could be the culprit to a dead short if not the link being pinched? I suppose it could also point to the voltage regulator since power routes through it? I have since looked to see if perhaps that fusible link could have been pinched between the battery and the rad support but can't see any spots where it arced or welded to metal? Don't know for sure but have traced the remaining wires which all look sound and have the original wraps on them with no evidence of any trouble spots?

I have ordered a repro battery cable but still, need to isolate the cause of this short before reconnecting anything or putting a new battery in it. I would appreciate any pointers from any electrical guru's to help chase down the cause or perhaps the most effective way to test the lines and or possible hardware that may be at fault? Any ideas or things I could be overlooking?

Feel free to reply, PM, or call me on my cell for any tips or suggestions.

Thanks in advance.
Graeme
403-669-4035


The fusible link after it melted down. It saw high current and fried in seconds (big cloud of white smoke)!


Where it appears to have started? Measures to the rust mark you see top right where it may have been pinched behind the corner of the battery?


The side of the battery where it was scorched by the wire (top right to lower left) that was draped along side of it.


Result of a very hot wire wrapped around the battery and melting through the case.
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Last edited by NorCam; 06-06-2020 at 05:11 PM.
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  #2  
Old 06-06-2020, 05:43 PM
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'

Crazy stuff but great you were there to save the car also that it wasn't in the garage.
Have you checked the wiring @ starter end yet as + wires w/ protruding tabs mounted clockwise incorrectly @ solenoid can sometimes short or it could be the solenoid itself or other wiring failure?
Best of luck figuring out what went wrong also getting everything back in shape!

~ Pete

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Old 06-06-2020, 06:53 PM
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Graeme
That SUX ! Just to be clear I do not believe that wire is a fusible link. There is a orange one I can make out in your photo coming off the distribution block, I think that one is for special insturmentation. There are 3 more near the VR, 2 orange and a black.
A fusible link would have opened completely up.
The #10 Red wire that fried just feeds the J block. If none of the links blew out, it is still possible the #10 wire is all that shorted, proceed slowly .

Mike, also a PM sent
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Old 06-06-2020, 10:29 PM
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If the melted wires stopped at the J-Block then the short is before the J-Block not after.
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Old 06-06-2020, 11:17 PM
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Default Be cautious

NorCam, I’ve been an electrician for 45 years and advise you to be careful. Get a good electrical diagram of your car to start with. If ya don’t understand it,stop and take the car to a shop that knows how to find out what happened. They’ll burn to the ground pretty fast.
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Old 06-07-2020, 01:15 AM
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Mike...

You're a good man! Thank you for the message and the materials. We're going to put the voltmeter to use tomorrow and will start checking the starter circuit and solenoid and work back from there until I find the cause. I'll check the fusible links on the other side to ensure they are all good also.

Thanks so much
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Old 06-10-2020, 05:38 AM
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Any luck finding the gremlin?

Jason
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Old 06-11-2020, 02:13 PM
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I sold Mark Bulaw a near NOS side post cable 8 months or so ago... it has printing on the brown wire which I thought said 14 gauge Fusible link, you may want to contact him, I cannot find my photos...
What ever you do - DO NOT THROW THE CABLE AWAY... the repro doesn't have the DELCO EYE - it just has a (+).
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Old 06-12-2020, 09:26 PM
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Haven't thrown out anything and will keep the original cable.

Traced it to being an old cracked wire that was pinched between the rad support and the battery. We found the spot where it went to ground and I'm still waiting for the new cable to arrive. Should be here today?

We checked all the wires in both directions as well as checked the solenoid and the VR before we found and isolated the spot where the wire went to ground. All good here.
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Old 06-12-2020, 10:43 PM
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Had that happen to me why I was driving my 69 z 10 years. ago. The front end harness had a short or rub through . I got a new harness installed and my insurance paid for it. That thick red wire in the harness carries a lot of power over to the horn relay junction terminal.
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