Faulty wiring

I was chasing a wiring problem on my 76 Vette, the rear compartment and glove box lights weren't getting any power, and this is what I found. What looks like an x in the picture is actually a pin hole in the wire that had to be there from the factory. The harness this piece of wire was in runs down the left side of the car under the sill plate and this particular piece was at the forward curvature of the door. It was obviously exposed to water and over time the wire corroded and the wire opened causing a loss of power to aforementioned lights.Attachment 58437

That one must have been fun to find! Power at the source, but nothing at the end, and continuity until you get to the break.

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Originally Posted by rspears

That one must have been fun to find! Power at the source, but nothing at the end, and continuity until you get to the break.

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That's an under statement, poor quality control at the factory

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Originally Posted by NTFDAY

That's an under statement, poor quality control at the factory

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Yeah, but it lasted 37 years......:HMMM:;)

I hate electricity in any shape except "working" - - - glad you found the culprit.

Almost looks like the dreaded sharp point on a test light inflicted the damage??? Or maybe a sheet metal screw got into it??? Good find, Ken! Electrical problems like that can be a real bear to chase down!

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Originally Posted by Dave Severson

Almost looks like the dreaded sharp point on a test light inflicted the damage??? Or maybe a sheet metal screw got into it??? Good find, Ken! Electrical problems like that can be a real bear to chase down!

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I thought about a sheet metal screw, but the screws for the sill plate are in the center of the plate and the kick panel doesn't have any. Could have been a test light, but I didn't notice any breaks in the factory wrap. I hate things that don't work when they're supposed to and I have a pretty good set of wiring diagrams and Chevrolet used the same color wire in a couple of different circuits which I thought was kind of strange. Anyway I've never seen an interior wire corrode like that.

Once again, are you really that surprised after 37 years?? That's a pretty good run for a 16 gauge stranded wire.:rolleyes: With a '76 machine you might consider a new harness.

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Originally Posted by rspears

Once again, are you really that surprised after 37 years?? That's a pretty good run for a 16 gauge stranded wire.:rolleyes: With a '76 machine you might consider a new harness.

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I don't replace things that aren't broken just for the sake of replacing. The harness in my 66 Mustang is ten years older and no problems such as that. Wire is only as good as the insulation an if the insulation becomes compromised there will be problems. Maybe all of the people should replace the wiring harnesses in the DC-3's they're flying as those harnesses are over 80 years old for the most part.:rolleyes:

36 years of compression cycles......getting in and out of the car loads the sill plate. When the wire is hot (hot day in SFG), the wire insulation is soft. Eventually, the wire strand works its way thru the insulation. The sill plate or the fiberglass surface under it are not perfectly flat so there are higher load areas. Takes time but it happens. Back in the olden days, the Corvette fit wasnt the best either. In 76 and 77 they were building a SP full of them.

Nice find, I'm sure that was fun to find. Generally if wiring hasn't been over loaded, exposed to high heat, or probed my a test light, it can last a long time. It's funny how a pin hole like that will let moisture in and the water will follow the flow of current and corrode everything in it's path.

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Originally Posted by NTFDAY

I don't replace things that aren't broken just for the sake of replacing. The harness in my 66 Mustang is ten years older and no problems such as that. Wire is only as good as the insulation an if the insulation becomes compromised there will be problems. Maybe all of the people should replace the wiring harnesses in the DC-3's they're flying as those harnesses are over 80 years old for the most part.:rolleyes:

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I guess I should have been more clear, Ken. After 37 years of unknowns you''re calling out the factory for poor QA/QC procedures. My point is that if you're that concerned you should probably just replace the harness with a third party unit and get some peace of mind. Who knows when someone probed that insulation with a test light probe, or even with a needle or sewing pin into the conductors trying to verify current flow to the back of the car. It's a good catch, and I'm sure it caused significant frustration to find that small section with the flaw, but I cannot see blaming the OEM for something after this much time. You did a great job, but calling the factory out for poor performance is hard to justify in my mind. You found it, you fixed it, and it's not GM's fault, IMO.

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Originally Posted by rspears

I guess I should have been more clear, Ken. After 37 years of unknowns you''re calling out the factory for poor QA/QC procedures. My point is that if you're that concerned you should probably just replace the harness with a third party unit and get some peace of mind. Who knows when someone probed that insulation with a test light probe, or even with a needle or sewing pin into the conductors trying to verify current flow to the back of the car. It's a good catch, and I'm sure it caused significant frustration to find that small section with the flaw, but I cannot see blaming the OEM for something after this much time. You did a great job, but calling the factory out for poor performance is hard to justify in my mind. You found it, you fixed it, and it's not GM's fault, IMO.

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Oh, I don't know about that, I knew guys when I worked at McDonnell Douglas that did some pretty crappy work and some of it I ended up redoing.

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Originally Posted by NTFDAY

...a pin hole in the wire that had to be there from the factory.

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Originally Posted by NTFDAY

That's an under statement, poor quality control at the factory

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Sorry, but after 37 years how can you state, unequivocally, that the pinhole was in that insulation from the factory?? Do you have some type of forensic evidence that ties down the date of the penetration? I know that over the years I've poked holes in a bunch of wires chasing current, so I guess that there are a bunch of cars out there with "...factory flaws..." and "...poor quality control...", even though the holes were poked by yours truly. As I said before, you found it, you fixed it, good job, but don't blame GM. Who knows what jack leg mechanic or electrician poked that hole, and at what point in time. Really???

Without ever seeing the car and wire bundle in question your opinion is pious at best. I spent over 30 years working in factories of one sort or another with more than half of that time in quality control and I have seen first hand a lot of inferior workmanship. And those in the UAW are no exception as I was once a member of that union myself working in the ranks and not riding a desk.
I didn't post this for accolades or to get in a pissing match with you or anybody else over whose fault, if anyone's, it is. I did, however, post it to show the effects of faulty wiring exposed to moisture over time.

Not sure if the 76 Vette is like my 72 Vette but mine has 3 or 4 separate wiring harnesses.
Don't remember off the top of my head but there are 2 or 3 different wiring harnesses just for the engine compartment.
One for the dash lights and one for the rest of the stuff in the cab, then there are some fiber optic's that go to some light down by the shifter for the trany and two other lights I don't remember what they are for. Atleast not with out going in the garage to see. I want to buy a one piece wiring harness and replace them all. I had bought two wiring harnesses and to it to a guy in Florida to install them.
Well before I took it in, the wiring looked like a rats nest near the fire wall. When I got it back it looked like a bigger rats nest then when it went in. That was a waste of about $600 bucks.

The 76, from what I've read, had a couple of things that were unique to that year. One is the steering column and the other, that I know of, is the seat belt inter lock that disables the ignition. Mine was previously rewired to eliminate the seat belt interlock and I still have to clean up the mess that was left behind and that will be a project for a later time. I plan to replace to glass fused fuse panel with one with blade fuses and that will be a project for next year and at that time I will clean up the harnesses and eliminate any wires that aren't needed or being used. Rewiring with a new harness is not cost effective nor would it suit my needs in my opinion. Mine still has the factory alarm that uses the vending machine type key, minus the relay that's needed to make it work, and I'm debating whether to eliminate it altogether.
I'm no wiring guru, but I can follow a diagram or schematic or make my own if necessary.