Wiring mystery

[evlblkrfl]

I've got a fresh set of eyes coming over next weekend to go over it. Hopefully we can figure this out then

 

[Dejure]

As I mentioned, if you didn't own this straight from the factory, there is no telling what the previous owners did.

For example, on my 78:

(1) The previous owner wired the choke straight to the battery, which kept the choke open, AND drained the battery every couple days.

(2) I pulled about 20' of various wires out that taped into everything under the sun. It was obvious a stereo was pulled, cheap, crap gauges installed, wires cut to the heater motor and backups, . . . .


There is no telling what a previous, electronically challenged owner might have done. Many a fused wire is missing on these rigs [and were replaced with unprotected straight wires to the battery]

As to a new harness, these systems are really VERY simple, making them easy to correct. If you're going all in on one of these rigs, learning the details of working with the electrical is a must, just as much as is learning the ins-and-outs of swapping an engine, transmission or what have you.

Add to those corrections a few rules. Ones like shielding the harnesses from abrasion, be it with tape (the tapes used are NOT sticky, they are simple wraps secured at the ends or various places along their runs. Of course, you can buy the flex tubing too.

In the end, those temporary jumper wires are ONE OF your best friends. You can, temporarily, feed the block with 12, though I'd do it through a breaker, just in case.

 

[evlblkrfl]

Im definitely finding previous owner questionable things but for the most part it appears pretty original. I probably just need to step back for a couple days and take a breather. Its just strange that its showing full voltage at the junction but nothing works without a jumper. Probably going to end up disconnecting the harness at the starter, alternator and distributor and pulling it up to where i can inspect the entire length of the harness

 

[Old Guy Bill]

There are complete wiring diagrams here on the Forum.
This is the '77 one..
Fusible link at the starter for the supply wire to the terminal block.
Another fusible link from the terminal block to the cab fuse block.
I don't know if this helps,, but it can't hurt

 

[PrairieDrifter]

Im definitely finding previous owner questionable things but for the most part it appears pretty original. I probably just need to step back for a couple days and take a breather. Its just strange that its showing full voltage at the junction but nothing works without a jumper. Probably going to end up disconnecting the harness at the starter, alternator and distributor and pulling it up to where i can inspect the entire length of the harness

Now that's a good plan.

 

[HatchEquip]

Take a old but good headlight run 2 wires from it as in a home made test light but this will also pull more amps hook it up at your test point and ground the other light wire and also hook your meter up at the same points and see what your results are. Does the light light up, does the voltage go away on the meter?

 

[evlblkrfl]

Problem resolved?? Well my brother came over with all his fancy Snap On stuff to help me figure out what's going on and like usual we got nothing. 12.2 volts at the block but zero power to the cab. So we pull the headlight switch on to test if the volts drop or do anything and as soon as we touch his tester to the junction post the damn lights come on and now everything is fine. We're not quite sure wtf happened but......okay, it works now. Im gonna have a beer

 

[evlblkrfl]

Appreciate all your help guys. I sure wish we would've found something wrong

 

[CalSgt]

Problem resolved?? Well my brother came over with all his fancy Snap On stuff to help me figure out what's going on and like usual we got nothing. 12.2 volts at the block but zero power to the cab. So we pull the headlight switch on to test if the volts drop or do anything and as soon as we touch his tester to the junction post the damn lights come on and now everything is fine. We're not quite sure wtf happened but......okay, it works now. Im gonna have a beer

I wonder if there’s a bad crimp on one of the wires at that junction block….

 

[75gmck25]

The wires from the starter to the junction block have fusible links. A fusible link that is overloaded may burn out inside, but the burn is nearly invisible from the outside (maybe a bubble in the insulation). Or it may partially burn, leaving only a few strands of wire connected inside. I think this may be the reason why you moved the wire around to make tests, and suddenly you have power again.