Burnt wire

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ajarofclay

ajarofclay

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Evening, gentleman. I found something very bothersome that I'm hoping one of you can help me out with. While trying to clean up my engine bay a little bit I came across this fried wire. I've owned this car for 50 years but I somewhat put it away over 30 years ago when I started having kids and chasing Sports Etc. I have no recollection of this happening and I think if I did I would have straightened the problem out and I haven't come across any electrical problems. I am the second owner, buying it when it was 2 years old. I can tell you that it had an aftermarket air conditioning system on it which I feel was a terrible install but I'm not saying this had anything to do with it, just that it did have some bizarre wires and hoses that were routed through the firewall. In case it's not clear to anybody this is coming from the plugs on the driver side of the firewall right next to where the trans kickdown is. I can find absolutely nothing anywhere near this where it would have connected to. Up close it appeared to be wrapped in black electrical tape but on further inspection I'm thinking that might have just been burnt insulation and the picture seems to bring it up as a blue wire . Do any of you more learned fellas know the answer? Electricity is my least favorite sport.

20240220_152805.jpg
 
What year is the car? Find a wiring diagram and see what that pin in the connector goes to. For 1970 it looks like it goes from the starter relay to the ammeter
 
Could be the fusible link. That’s what it looks like being a little way from the bulkhead connector.

Often the connectors in the bulkhead connection overheat and melt stuff, usually due to corrosion.
There are basically three wires that usually get heat damage near the bulkhead connector.
1. The big power wire (fusible link) going to the amp meter on the dash in the passenger compartment.
2. They big wire coming from the amp meter into the engine compartment
3. )The ignition wire
 
Looks like its a shared terminal (two wires crimped to one terminal)

Some years that position is for the J2 (ignition run) and the wire color suggests that might be the case here.
 
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Craig, Sorry, I neglected to mention the year/model. I always get aggravated trying to do this stuff on my phone. Car is a 1972 Demon 340 w torqueflite.

str12, no the wire isn't touching the kickdown, I know it kind of looks that way. It never was though. It's just wierd that I can't see any sign of the other end of it.

Mike, I don't believe it's the fusible link, I think I felt that in another part of the loom, I'll check and get another pic later.

Mattax, Yes, it definitely looks like it's two wires coming from the second cavity down on that plug. I'll try and get my old *** underneath the car later and see if there's a wire loose down there.

I can tell you all it does turn over though. Not ready to fire it up yet but I could see if the plugs are getting spark.
 
I'm 99% sure I found the problem, gentleman. I had to dig through some boxes and found an old manual on CD. From what I see that terminal should only have one wire going into it. I chased where that wire goes to and found it basically splits between a ground and the ignition switch in the interior and then under the hood going to the ballast, alternator Etc. So I pulled out that aftermarket air conditioner that I had packed into a box and looked at the wiring on that. The black one in the picture by my thumb came through the firewall at one time and just the last half inch of it is hard as a rock while the rest is pliable. Like I mentioned before I thought it was a horse bleep installation.

20240221_105720.jpg
 
ajarofclay said:
I had to dig through some boxes and found an old manual on CD.
Click to expand...
If that works. Lets use it. Otehrwise you can download one from mymopar.com
ajarofclay said:
From what I see that terminal should only have one wire going into it. I chased where that wire goes to and found it basically splits between a ground and the ignition switch in the interior and then under the hood going to the ballast, alternator Etc
Click to expand...
Nothing should be grounded!
Ignition switch going to ballast, alternator field, etc is the Run circuit. In the shop manual the run circuit wires are identified as J2. Branches and segments are J2A, J2B etc. The - Wire gage and color.

For the bulkhead connectors, there is a photo in the Plymouth shop manual. That will help with orientation when looking at the car for real. Note on the engine side each connector a bump out to further help with orientation.

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So I think you are looking at position N.

I'm on a laptop with somewhat limited internet now.
So check out this post for a what I think is the '72 diagram which does show J2 going to N.
Cavity P has the alternator output R6-12gage Black. That is hot. Connected to the battery positive.
Position J should have the fusible link. Be careful with both of those.

I would look at the fusebox for an accessory slot that can be used for the A/C. That's what the factory did for A/C power in the 60s. Not sure about later.

But first get your J2 circuit squared away. Its a critical circuit. Too much load on it and the regulator will see low voltage due to resistance. It will correct causing the alternator to output at higher voltage than it really should be. This cooks the battery.
 
Thanks for that follow up. Again, I'm lost on electrical. I just followed the schematics for where that lone wire was heading. The ground it showed was after that line split somewhere. I attached the pics. The burnt wire I'm confident was installed there for the (supposedly) the correct type of active connection. Who knows if it actually was. I should have pulled that system off when I bought the car.

20240221_103020.jpg


Screenshot_20240221_104435_Gallery.jpg


20240221_110128.jpg
 
There is no ground!
Not in the diagram. Not in the operations.
Take the A/C out of the picture to begin with. Fix the run circuit first. Make sure nothing is grounded. J2 Ignition run - It is NOT fused. It is only 16 gage wires at best so will burn before the fuseable link.

Read through the link I provided.
1972 duster engine harness ECU electronic ignition The circuit codes are actually pretty easy once you understand the format. There's a late 60s MTSC on how to read and use the diagrams if you need.
 
Mattax said:
There is no ground!
Not in the diagram. Not in the operations.
Take the A/C out of the picture to begin with. Fix the run circuit first. Make sure nothing is grounded. J2 Ignition run - It is NOT fused. It is only 16 gage wires at best so will burn before the fuseable link.

Read through the link I provided.
1972 duster engine harness ECU electronic ignition The circuit codes are actually pretty easy once you understand the format. There's a late 60s MTSC on how to read and use the diagrams if you need.
Click to expand...
I understand that. What I was referring to is if you look at the middle schematic you can see where the J2 splits at whatever the Diamond w 3? is. That run becomes G5 which goes to the dash and 9 pin connector THEN appears to go to a ground. Again, I could be wrong as there probably aren't too many peeps on here that know less about electrical issues than me. That said, I cranked the car over yesterday and it does have spark so I'm feeling good about that. Can't try to run it as I have a lot of stuff disassembled, carb, hoses, etc. I do know that there is only one wire that should be coming out of connection so I'm pretty confident the extra wire was for that aftermarket AC and I've removed that. Also, the dash at least as far as lighting and switches all do there job.
 
ajarofclay said:
What I was referring to is if you look at the middle schematic you can see where the J2 splits at whatever the Diamond w 3
Click to expand...
The diamonds represent junctions - usually splices. Sometimes we'll find the junctions done at terminal instead - probably because production found it easier.
Older diagrams will show welded junctions as solid circles, and connectors as open circles.

So that is supposed to be a welded juntion - and it looks like that drawing is the instrument panel harness.
I think the artist labeled the segments backward from how they work. Seen this in a couple years.
See if on your diagram J2B - 12DBL is coming from the ignition switch.

ajarofclay said:
That run becomes G5 which goes to the dash and 9 pin connector
Click to expand...
Yes. I follow you. G = Gages.

ajarofclay said:
THEN appears to go to a ground
Click to expand...
I see why you think that. I remember that drawing being a little hard follow.
The G5 wire is connected to the "12 V" tracings on the circuit board (dashed lines)
Ground refers to the ground of the Instrument Voltage Limiter. The IVR has system power available at the bottom connection, ground on the left connection, and "5 V" output on the right connection to the board.
1708697065787.png
 
Mattax said:
The diamonds represent junctions - usually splices. Sometimes we'll find the junctions done at terminal instead - probably because production found it easier.
Older diagrams will show welded junctions as solid circles, and connectors as open circles.

So that is supposed to be a welded juntion - and it looks like that drawing is the instrument panel harness.
I think the artist labeled the segments backward from how they work. Seen this in a couple years.
See if on your diagram J2B - 12DBL is coming from the ignition switch.


Yes. I follow you. G = Gages.


I see why you think that. I remember that drawing being a little hard follow.
The G5 wire is connected to the "12 V" tracings on the circuit board (dashed lines)
Ground refers to the ground of the Instrument Voltage Limiter. The IVR has system power available at the bottom connection, ground on the left connection, and "5 V" output on the right connection to the board.
View attachment 1716211149
Click to expand...
Dang, that's a bundle of knowledge! That's why I depend on this site for people smarter than me. I appreciate all the great insight. I thank you again.
 
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