Technical Electrical fire/battery issue

I’ve recently been having issues with starting and thought it was from a faulty battery. I swapped it out with a freshly charged battery, and same thing, it would hardly crank. I noticed my generator light was very dim and then i heard some crackling. Soon enough there was a flame directly below my vent knobs In the cab. I put out the fire and searched for the cause. The vent cable itself burnt in half (this is not an electrical wire.) there was a wire that was slightly pinched, touching the vent cable, but I couldn’t see a break in the wire insulation.
I went over all of the wiring, and all seemed good. I also checked to see if any electrical connections were touching the vent cables...nothing. Later on i tried starting the truck again, and a small arc was occurring between the vent cable and heater. I disconnected the battery and touched the vent cable, and the cable was scolding hot. My heater was turned off so I’m lost on what’s happening. Any ideas on what the issue could be?


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Maybe something is getting ground through the cable, because it's normal ground path is broken?

 

Yeah, your vent cable has been acting as your engine ground cable. Make sure your battery ground is securely attached to your engine block and that the connection is clean. If your ground cable runs to the truck's frame, install a ground strap from the engine to the frame....make sure all connections are CLEAN! I like to coat the connections with dielectric grease to keep corrosion away

 

Good grounds are your friends.

 

I agree with Rocky and Squirrel, vent cable has become your ground.
"Rocky and Squirrel" that's just too funny

 

Yep, I’ll have to chime in on faulty ground. Any time something is crazy.....look for bad ground!




Bones

 

Grounds will use any means to make themselves happy, screw your nice truck. I would look for more trapped wires before reconnecting the battery.

 

I've seen many variations of Lack of good ground travel over the years. Yours looks to be just the latest one.

 

Ground frame to the block and ground the body to the frame, your cable was acting as a ground. HRP

 

Like the floor shift cable burning because the block and frame ground is not proper.
Like ice cream never to much.

 

I read a lot of different automotive forums, and loose, missing, or corroded grounds and cables cause all kinds of issues. Glowing brake lines, red-hot throttle cables, roasted voltage regulators, wheel bearing failure and internal radiator damage are a few of the "interesting" failures. I'm sure there's more. The engine starter typically draws 100 to maybe 200 amps and this is where real damage can happen, because in the absence of the correct ground straps it will draw those amps through something never designed to carry any current.

 

I was at a KOA campround near the SR Nationals in Lousville in 2000 I think it was. Neighbors in camp were trying to start a Rod. I went over to see it, then yelled at them to stop cranking! Why? they asked. Because your throttle cable is smoking! I told them they didn't have an engine ground. One guy looked at the other and asked if he had put that ground back on? Nope. Fixed the problem and we got free entry into the rod run.

Dave

 

Thanks for the advice! I just checked and i have a #4 going from battery to the firewall. From a different point on the firewall I have a braided strap going to the block. I can’t find anything going to the frame. Do these points of grounding sound adequate plus an added ground to the frame?


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I never understood why the OEM would run the battery cable first to the frame? I want the engine block first, maybe somewhere around the starter. Then on to the frame, and one more from block to firewall.

Sometimes it looks like the manufacturers treated copper as a semi-precious metal, with short, puny gauge wire, just barely up to the task when new.

 

One can never be too grounded.
A glowing choke cable taught me.

 

I run battery cable to the block, block to the frame . Body to frame or block if the body is steel....another animal if fiberglass. I had the frame/engine grounds on a '36 Chev p/u, everything seemed to work but the gauges were erratic on the way to Louisville Nats....new build, old gauges. Was looking to replace with underdash set of S/W while I was there, then I thought of a ground to the body. Bingo! No problem with the gauges.

 

Also, make sure all ground points are bare metal to metal....a lot of problems with new builds because of paint!

 

I replaced enough Pontiac floor shift cables in the 70's and 80's because someone had changed the valve cover gaskets and left the ground straps from the valve cover bolts off that I lost count.
Grounds may be the issue but on that one I would have to think that you have more than one 60+ year old wire with failing insulation that is making contact where it should not make contact.
I'd agree on making sure the grounds are good though. I've had a guy cry because I took my knife and scraped the paint away where the ground strap needed to be contacting the block, frame or body because I "ruined" his paint while fixing the problem he asked me to help fix.

 

I understand the Paint issue. If you use the right kind of lock washer you don't need to scrape off paint. A standard cut style lock washer won't get it. These come in every bolt size out there and will do a much better job without touching the Paint job.