1948 John Deere B - Electrical Gremlins

I thought about posting this in the John Deere forum, but I figured there would be plenty of tractor enthusiasts with electrical expertise that could contribute if I posted here...

My father recently complained to me that his old B wouldn't start. He went on to say that it refused to start last winter as well. So he and I took a stroll up the hill to his shed where my grandfather's B sits in storage...

With a fully-charged battery (6v positive ground), my dad cranked the engine over. The smell of varnished fuel rolled slowly out of the exhaust and the engine refused to fire. We pulled the sparkplugs and made a note of how clean they were; a light carbon haze, but not oily. We tested for spark; none. My grand-dad ditched the magneto decades ago, so we decided to inspect the points. We began to remove the distributor cap when I noticed the wiring...

With the exception of the heavy-gauge wires from the distributor to the sparkplugs (and the battery cables), every inch of wiring on this B has its insulation burned off. Black, twisted, and curled...every wire has charred insulation hanging off of it and bare (green) copper is showing. Obviously there has been a serious electrical current flowing through these wires. A dead-short somewhere?

We'd like to respectfully request some insight into what the culprit(s) may have been.

We've started rewiring the tractor, but we'd like to avoid this issue happening again. We feel fortunate that my grand-dad's B didn't burn to the ground.

Very likely nothing but mice. Check for nest up behind dash/guages. Even their pee and crap will eventually conduct electricity where it shouldn't be.

I appreciate the reply, and mice or other rodents would certainly be a possibility. We haven't located any nesting materials or evidence of mice, but I certainly have experience with the damage rodents can do to ATV electrical and airbox systems...seems very possible that the same could be true of this tractor, even without obvious signs of their presence.

Since it's all burned now , you will probably never know what exactly caused it. Could have been just old brittle insulation that cracked at just the same place where it bent around a good ground source.