Melted wires everywhere… need some help

Long story short, 86 stepside 5.0,
1976 350sbc installed by last owner with an accel distributor, man choke 1405, and a lot of melted wires. Need suggestions on what to do about the cut wires from the firewall (yellow arrow). I’m guessing it goes to the heater box that has badly melted wires. I can’t find any specific replacement harness for them. I’m guessing there isn’t one?
Pic 3 is an unused plug than I’m unsure of and pick 4 is also unplugged. What do these go to?
I ran the truck yesterday for about 20 minutes and shut it off. Half an hour later, I went to start it and it clicked once and then now it’s completely dead, no interior lights, headlights etc. with a key in the run position, the battery gauge will come on and show good voltage, but the second you try to start it, gauges shut down. I’m guessing it’s a fusible link? Do to the fact that I have a brand new battery and starter and ground wires. Should I try to make a new fusible link? Or I’m thinking about rewiring all the power wires/ crank wire all the way to the junction block. I plan on LS swapping in a few years but would hate to spend a lot of money on a painless harness that I won’t reuse.

And on the last pic, does anyones shock to frame mount look like a nine-year-old welded it?
What would you do about the cut wires and melted wires to the heater box? Thanks for the input.

Anything under the dash melted? Maybe try a salvage yard or bite the bullet for a "Painless" solution.

Those don't look like the right spot to be AC wiring. That looks like the ESC wiring that would be in place on an 86 305 motor.

I would start by down loading the wiring schematic for your truck, study it. Go over the burnt wiring and make notes of what circuits are affected, look for a pattern. Is it only affecting the engine compartment, is it affecting under dash wiring, is the lighting circuit affected. figuring out what is affected should help you find the location of the short. PO could have cut the wires going thru firewall to remove the short, but never replaced the burnt wires.

Find the short before replacing the harness so you don't smoke the new one. You will need a multimeter/voltmeter to trace down problem. A test light will help find voltage, meter will help find shorts.

It looks like the shock mount was broken and welded by someone that does not weld for a living, looks fairly secure, but not pretty.

I have the diagrams now, and I’ll try and track down the problems. Do you know if any literature that would show resistance between circuits or ohms?

greene said:

I have the diagrams now, and I’ll try and track down the problems. Do you know if any literature that would show resistance between circuits or ohms?

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The electrical manual for an 1986 or maybe the service manual may contain diagnostic flow charts for problems but tthats about the only thing I could see Maybe doing that. You dont need to know a lot of resistances except for things like checking switchs or ignition coil

voltage dropwould be better likely anywasy

@greene, a little context would help diagnose. Like wires been melted for however long? Heater/AC still function?
Your issue looks like someone direct wired or used far too large of a fuse, or something similar where a live short didn't blow a fuse before cooking wires.

From what I see the the melted wires are blower motor/relay/resistor block. All 3 of these items are available and cheap.

The power for the highest fan speed is direct from the junction in the firewall. No fuse. If shorted. **** melts.

Grit dog said:

@greene, a little context would help diagnose. Like wires been melted for however long? Heater/AC still function?
Your issue looks like someone direct wired or used far too large of a fuse, or something similar where a live short didn't blow a fuse before cooking wires.

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I’m unsure how long they have been like that, I got the truck about a month ago. Heater doesn’t work and there is no a/c compressor.
I’m going to start replacing wiring soon, I’ll probably use a painless kit.
I just wanted to drive it some before something major like that.

wlwarnke said:

The power for the highest fan speed is direct from the junction in the firewall. No fuse. If shorted. **** melts.

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....added "Put fuse on heater fan wire" to my **** to do list now!

Grit dog said:

....added "Put fuse on heater fan wire" to my **** to do list now!

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Luckily that wire is fairly short. Junction, to relay, to fan. I’m guessing 40-50amps? I haven’t seen a rating on those fans as far as watts or amps.

The blower motor probably doesn’t pull more than 15-20 amps tops during operation. It pulls probably twice that during startup.

20

Well I replaced numerous wires with proper gauge and tested the fuseable links and made sure my grounds/fuses were good. Still will not start. Test light shows power to the junction block, starter and hei (with key on).
I can turn the key to on and the battery gauge works until I try to start it then goes dead. I can also kill the battery gauge if I touch the headlight switch… not sure where to go from here.