Electrical Voodoo Wire⁷

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This tripped me up today.

Service truck went down, as in now it is an over priced rolling toolbox. No PTO, no air compressor, no crane, no lights.

Verified no power at the service body module in the rear compartment.

Turn the PTO on and it killed the engine. Would not restart with the parking brake on - dead dash.

Open the primary circuit breaker for the service body and then the truck would stay running.

No road map. It’s 0400 at the corner of NO and WHERE Nebraska.

Follow the primary power wire from the engine compartment and it goes under then into the cab behind the seat. Great, a module that is plugged into the truck. Power in, nothing out. No blown fuses, all diodes and mini breakers OK.

Disconnect the truck from that module and now I have power in back, power in the rear module, nothing out. Test the ground and it’s hot - ah ha.

I check the connections (stud and the bolt it’s on in that compartment) and I get a brief flash of my compartment lights. I put in a ground jumper from my jumper cable connection in back and I have lights.

I pull the ground wire and try a different ground point and still nothing.

Now the weird voodoo stuff.

I ohm out the wire and I get this

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Negative ohms means there’s power in that circuit. WTF?!? It’s a wire. I test my meter, verify against other 0.0 resistance items and the meter is working as normal, check the wire again and I get the same reading. Flip over to volts and I get this.

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I try touching the ends of the wire to short it out. Nothing. 5 minutes later it is still giving me that reading.

Somebody can explain this, I am sure. I need to know. Right now I am blaming the Indian Burial Ground that our batch plant site is on (all manner of electrical weirdness going on for the last year). Baring some sort of verifiable scientific explanation I am going to dig a 10’ deep hole with an excavator and plant this wire in it and bury it.

Nothing special. Marked 10ga primary, not a fuseable link (on a ground?) simple heat shrink crimp eyelets on the ends.

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What if to touch your two meter leads together with it set in the same position?

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This did include touching the leads together on Ohms and volts. That was the first thing I did

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Very weird, you should check it with another meter. So you think this wire is the problem? Did you make up a new one and try it?

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I did verify against another Fluke.

Also made a replacement, fixed my truck. The VooDoo wire is in containment with a bundle of sage and stump water to be safe.

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That was a good catch, you should be proud. I am 99% sure I would have never checked that wire for continuity as it looked good. I know I know cant go by looks. Problem with that kind of stuff, I would now want to know how that could happen and would start down the rabbit hole.

That is some awesome trouble shooting. My hats off to you!

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Definitely Alien territory! :alien:

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It must be the new wire that is coated with a rubber-like substance derived from corn that the rats like to eat.

Sounds like an electrolysis phenomena.

Glad you got it fixed!

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You can get some components that go bad and a process dubbed as backfeeding voltage. Rare but it does happen. Ive only seen it once in the 16 years Ive been a mechanic

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Backing feeding was probably more common back before computers were in cars. Wiring in American cars has come a long long way since then.

Location would also play a role in it, if your somewhere where they use a lot salt on the roads help create corrosion problems that lead to back feeding.
When I was younger every once in awhile you would see a car with a tail light that might glow dimly when it shouldn’t and that was sometime related to back feeding

But in this instance it was the source of back feed. I have never seen anything like that.

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Yeah, that tripped me up, and lucky I found it. Just test the simple things, simple as in easy to get to and little work involved.

I deal with tons of high resistance issues on ground and power circuits. Just keep testing at the source, destination, and any connections available in between that can isolate the problem to a small location.

Age of what you are working on also plays a factor in what you are trying to solve, along with envrionment and exposure.

In my case, this is a 1.5 year old truck and service body, and both modules and all the wiring and connections are in protected environments - one in the cab of the truck, the other in the rear compartment. Not as protected as I would like - lots of dust - but free from water other than humidity.

This particular wire, sealed on both ends. Not the typical open end heat seal connector. 1.5 years old, protected from the environment. Problem free up until now.

Still waiting for one of our rocket scientist, classified DARPA employees to explain how a simple 10ga stranded copper wire, with sealed ring terminals on the ends can turn into ha high resistance conductor that happens to be able to mimic a battery that can not be discharged.

Pretty sure the trace elements that are necessary for making a power storage are not present in the components used.

Low current on that circuit as well. 10a at most, and that is the LED lighting. All of which shares the common ground point in that compartment.

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Just curious were you working the trucks electrical hard recently. Wondering if the weak connection didn’t get hot and cause the wire to fail.

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No, this is my service truck. Not much night work so the light’s which would be the heavy power draw don’t get used much. Normal day to day use would be around 1-2 amps (speculation) for the crane control and wireless remote.

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The car I saw it on was a 2008 Honda Ridgeline.

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Sometimes if there’s a bad or weak ground connection it will back feed stray voltage.
Stray voltage is like Voodoo

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Backfeeding I can deal with. How is it [voltage] staying in a disconnected wire shown in the pictures.

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What ever the other end is connected to my have a capacitor in it? Like I said Voodoo.

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What you had was a new form of Voodoo it involves AI. We should all be very afraid :grimacing:

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Corrosion between the conductors in the wire is giving it some capacitance, getting a slight conductance charge from a nearby ac source like a power line or motor. I see this at work on a larger scale on our equipment on high tension line towers. If I was a betting man, I would say one of those crimp connections were bad.

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Good to know. Thank you for the insight!