Mystery Electrical Fire!

[HIGHWAY BY THE SEA]

Something VERY strange happened to me on April Fool's Day (no joke). I was driving my 68 C10 out in the sticks and as I stopped for a red light, the engine just DIED. I tried to start it, but it just turned over and over, but would not fire. I pushed it into the parking lot of a gas station that just happened to be right there, and popped the hood. I noticed some gas that looked as if it had leaked out of the carb, so I figured it was flooded. So I waited a full hour, then attempted to start it again. It fired up when I floored the pedal, so I got out of the cab to close the hood and go on my way. The first thing that I noticed was SMOKE coming from the wire that goes from the junction block to the positive battery cable. I dove headfirst into the cab, killed the ignition, flung open my toolbox that was on the floorboard, grabbed my channel locks, and yanked off the positive wire. But by this time there was a small wire fire right in front of the battery (which I blew out like a candle). Now the damage. My entire wiring to the alternator was FRIED, the wire to the junction box was burned through, and the wire that ran from the battery junction box to the firewall junction box was fried (which in turn also fried my light harness). I have NO idea what caused all this. I replaced the battery 2 days before this and drove the truck 175 miles, and it was on the day AFTER this trip that this occurred. Any ideas on how this happened?

[ray_mcavoy]

That sounds like there was a dead short to ground somewhere in that main feed wire that connects the battery, alternator, and powers the truck's entire electrical system. It could have been a wire that was rubbing/chafing somewhere that finally wore through and shorted out. It might have been a momentary short at first (enough to kill the ignition and stall the engine). Then with a little bit of movement (created by the engine re-starting) the wire touched ground and shorted out again, and stayed touching longer this time, causing it to get hot and melt.

Dad had a similar wiring harness melt-down in his '63 Impala years ago that we traced back to a screw that had come loose inside the alternator and created a short to ground. Luckily, the damage was contained to just the wiring harness. The '63 wiring did not originally have any fusible links to prevent this sort of damage to the wiring but I made sure to add one to the replacement wiring. Your '68 should have had a fusible link connecting the positive battery terminal to the nearby junction block on the fender that would have protected the rest of the wiring. But a previous owner may have unknowingly replaced it with a section of regular wire.