What would cause melted blue/white wire under dash at “N” terminal on bulkhead?

[AZMoparJoe]

Car is a 69 Coronet. I relocated my bulkhead wiring at terminal “N”, “P”, and “J” out of the bulkhead. While I was working on the wiring under the dash, I observed the blue with white tracer (from terminal “N” to ignition switch) partially melted. The wire going from the bulkhead to the alternator is in excellent condition. What could cause this? The car has had a squareback alternator and a proper 70-newer electronic voltage regulator as long as I’ve owned the car, and there have been no issues with the charging system whatsoever. Any ideas as to why this short length of wire is melted and everything else is pristine? I ran a new wire from the ignition switch to the firewall/bulkhead and the wire is not getting hot while running the car.

I think I’m going to go through the entire bulkhead and replace the female terminals with Packard 56.

 

[pnora]

Either a short to ground at some time or high resistance due to loose connections.

 

[65CopCar]

What car?

 

[AZMoparJoe]

What car?

1969 Coronet

 

[72RoadrunnerGTX]

As mentioned, the car likely experienced a short on ignition 1 in the engine harness at some point in the past. If you replaced the wire with new wire of the same size and the wire is not heating, the short condition that caused the damage may no longer exist. I would still inspect the ignition 1 circuit/wiring in your current engine harness closely for possible intermittent shorting somewhere. That particular ignition 1 bulkhead Packard terminal (N) I will typically bypass, along with the charge parge path Packards (J&P), as any voltage drop developing there will mess with the regulator reference voltage, causing higher than normal battery charging voltage at the battery.
Of all the unfused wiring being protected by the stock 16ga fusible link, that ignition 1 run from the ignition switch out to the engine harness ignition loads are the smallest wire size at 16 & 18ga, they will melt down as a result of any short circuit in the engine harness before the fusible link opens. Fairly common to find those wires on that circuit burned.

 

[dadsbee]

Just another day in MOPAR land...

 

[Nirvana]

It’s called Karma for screwing me out of $100.

 

[65CopCar]

So where was it melted? I looked at the wiring diagram and it gets a little fuzzy. Looks like it feeds the ignition and the alternator field from the ignition switch. Could be something going on with the filed or ignition. It also taps an 18 awg gage wire that goes to the instrument cluster. Don't know what it feeds from there.

But it could be a bad connection at the bulkhead - that is why where it melted is important.

 

[AZMoparJoe]

It melted from the bulkhead to the ignition switch. Not completely, but it has gotten hot at some point in the past. All of the underdash wiring and engine compartment wiring is pristine with the exception of that one wire.

 

[pnora]

It melted from the bulkhead to the ignition switch. Not completely, but it has gotten hot at some point in the past. All of the underdash wiring and engine compartment wiring is pristine with the exception of that one wire.

Maybe the engine harness was replaced before you got it.

 

[AZMoparJoe]

Maybe the engine harness was replaced before you got it.

Definitely a possibility. I guess I’ll just keep an eye on it. Like I said, I’ve had zero issues during the entire time I’ve owned the car. It’s just puzzling how one side of the bulkhead has a melted wire, and the other side doesn’t. Mopar mysteries!

 

[jimbosride]

Just on a side note, all my classic cars have one of these on it

 

[pnora]

Definitely a possibility. I guess I’ll just keep an eye on it. Like I said, I’ve had zero issues during the entire time I’ve owned the car. It’s just puzzling how one side of the bulkhead has a melted wire, and the other side doesn’t. Mopar mysteries!

A short always burns back to the source of power. My bets there was a short to ground and that circuit burned up the engine side pretty good and warmed up the dash side. They replaced the engine harness and did nothing on the dash harness.

 

[Bird 426]

Probably looked like this.

 

[terrywalker]

Found this on my 72 Challenger last year. Doing the wiring change to bypass the bulkhead connector on the car. Avoided a disaster by checking things over. I'm glad you found yours. These old cars can have some hidden electrical problems.
Terry W.