Hi guys,
I took a short video of the problem I am discovering as I start to tear into the stang.

It shows some burnt wires that will likely need to be addressed or bypassed. A large black wire from the battery lug of the starter solenoid is burnt and a wire going to the alternator is burnt. There are two mystery modules in-line that you'll see in the video that I need some clarity on.
Thanks!

 

Background about what was going on when the wires burned would be helpful. The yellow and black wire goes to the center post on the back of the ignition switch. It is always hot and vulnerable to shorting, especially when performing maintenance on the ignition switch itself. The yellow wire with it at the black block, which is a factory splice appears to go to the amp meter in the instrument cluster, and there appears to be a green and white striped wire that also connects at that splice that goes to the center of the alternator plug. Below is a wiring diagram.

 

Yeah I wish I knew the background too! I can look at the back of the ignition lock cylinder. I did change that out, but didn't look at the wiring harness coming up to it that closely.
Any idea on the inline "joints" where the wire colors change? Can I just cut those out and splice wire from the other wire colors back up to the battery lug on the starter solenoid?

 

I am also trying to work my way on the that diagram back from the ignition coil, following wire 16. I see it becomes wire 16B and 16A? I am wondering where to locate those connectors 14401 and 14290 to see if there is a problem there? Is that up under the dash somewhere? And after connector 14290, I can't tell which wire turns into 16.

 

On the last diagram the connectors are designated with a letter in a circle with lines pointing to each connector. The diagram below shows (kinda) where the connectors are located. It's a little fuzzy which side of the firewall some of them might be, but I think it is still a helpful drawing.

 

Speaking for my '66, the 16B is the power wire to the coil and it is either powered directly from the battery, through the ignition switch while cranking, or through the ballast resistor, also from the ignition switch when in run. The "D" connector on my '66 is the firewall penetrator - half in the engine bay, half under the dash. There is an additional connector on the '68 diagram, "C", that doesn't exist on my car. The ballast resistor is recommended to be removed when using Pertronix electronic ignition. I had to locate that connector when I did that mod a few years back.

 

Ah cool, where is that ballast resistor? Under the dash? I guess I see that little squiggly line on 16A coming from the ignition, is that it?
Thanks so much for your help! I really appreciate it.

I forgot a piece of information. I have installed a 1 wire alternator w internal voltage regulator and removed the factory voltage regulator. It doesn't look like I'm missing anything by removing it, according to the diagram....I think? lol

 

The ballast resistor is the wire itself, and it is spliced directly to the direct power coming off of the switched pole of the solenoid. I believe the splice is in the connector at the firewall, it is on the '66. So 12V comes from the solenoid while cranking (to the coil), then reduced voltage comes from the ignition switch when in run. Also while in run, the ballast resistor wire sends unused power back to the switched pole on the solenoid. I figured this out when I removed the ballast resistor and lost the power to my electric choke, which I connected to the switched pole on the solenoid.
In regard to replacing the splice and wires. That depends on the condition of the wiring between the splice and the ignition switch. If it is in good condition, I personally would try to salvage about an inch and a half of the two wires coming out of the splice, shrink wrap half of that from the splice out, and make good soldiered and shrink-wrapped splices directly to the two remaining wires. You would have to validate that the wires continue to have good continuity. The best might be to find a Stang being parted out, or at a wrecking yard (if there are any anymore), and harvest the section you need that includes everything between the solenoid and the splice, and as much of the other side of the splice as you can harvest from the donor vehicle.

 

Ok looks like on the 68, the connection at the starter solenoid has all the large ring connectors on the battery side of the solenoid. The only thing on the switched pole is the starter motor.

I patched that wire temporarily that was burnt with the same gage wire and temporarily wire nutted it together to test. I'll hopefully solder and shrink wrap that connection later, if things work out.

I also had another question! The old ignition coil had a "bat" and "dist" terminals labeled on it, the new coil just has a "+" and "-" and I just wanted to clarify that I'm hooking the "+" to the battery side wire and the "-" to the distributor side wire...

 

Yeah, I always have to go and check that one to be sure. The "+" side is the incoming power, or you're #16 wire. The "-" side goes to the distributor. If you have a volt meter, BEFORE you connect the battery, there may be some value in checking for resistance between the battery side of the solenoid and ground. There may also be a benefit to do that check with the key in run and even start if you can reach the key and see the meter, again, before you reconnect the battery.