Van fires!

I have read in a couple of places where a specific wire, due to it being a pathetically small guage, has burned through causing a fire to ignite, destroying another nice van. Does anyone remember which wire it was? Feed wire from ignition to starter relay? 2ndry wire to distributor? I have the van in the garage , for an engine swap, and thought I’d replace that wire specific and add a fuse.

I think the feed wire to the starter solenoid is the culprit... thx.

Since the horn relay is in charge of the electrical system, on a 1st Gen, you want to install a 14 gauge fusible link at the positive battery cable on the starter solenoid then connect a 10 gauge wire from the link up to the screw on the horn relay,,,,,so if something shorts out on the van, the link burns and disconnects the battery,,,,,,,unless,,,,,someone has added stuff to either end of that positive battery cable,,,,,,

No relays previous to about 1970 and almost everything essential was unfused other than these fusible links (if you've got them)..... The wire you refer to is the one that has it's own post on the starter solenoid and momentarily energizes the coil while the starter cranks......Fire-wise, I'm mostly wary of the fat positive wires going from the starter hot-post to the dashboard and alternator.... especially where they connect at the underhood harness connector along the left-top just inside the lid on first gen, and at the pass-through grommet on second gen..... Those connector plugs are not waterproof and eventually degrade and corrode and get hot and melt into each other or the connections degrade and get hot and melt stuff.... On mine, I'm going to run all engine harnesses into the cabin to make connections (dry and cooler) and have organized busses on the right wall for all my power, ignition and ground circuits ( in the right "108" wall above the battery)....I'm going to put the entire panel on a swing out hinge, so it can be worked on standing up at the side door...Fuse panels with push-button ATC circuit breakers and battery full-disconnect switches with removeable keys in the metal box panel below ( the one with the screw cover that accesses the inside of the rocker panel....)
Power from the batteries for everything (excluding the starter) will be routed through the right rocker panel to the master switches ( all metal enclosed, nothing flammable)...

Thx guys... all useful information. Just what I was looking for.

The horn relay on a 1st Gen, 1964-66, Chevy van is in charge of the electrical system,,,,,it is where the power from the positive battery cable connects to the van,,,,it is where the voltage regulator senses the battery voltage and tells the alternator when to start charging, and when the alternator starts charging, thats where the output of the alternator goes to the battery,,,,,thats also where the ignition switch and fuse block gets their power from,,,,,,so this little guy is pretty important,,,,,,

Does anybody have a factory schematic for second gen (69)......Mine harness is pretty scattered and I need a schematic in order to figure out how I want to update and add to it...

Which one you want 1st,,,,,Front end, Dash, Doghouse or Fuse block?

I got stranded once and I had to fix that voltage regulator roadside to get home. After I got home I replaced it and it got fried immediately. I got the wiring schematics from this site and found out they had some wiring wrong and replaced almost all the wiring for the ignition system, alternator, and voltage regulator. There was evidence of melting at that connection too, and I eventually replaced some of that wiring as well. Electrical is much simpler to diagnose but it is so much harder to replace on these old vans being all separated with all the various connection types.