Fried wiring

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Steve Mcbean

Steve Mcbean

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Location
Austin Tx
Hi fellas. I havent been here in a while, since my car was in the shop for upgrades for 16 long *** months. I got the car back with nice upgrades, but also more problems than before. For one, there was a short somewhere under the dash and the car wouldnt start without wiggling group of wiring under the dash, so I called a mobile mechanic here in San Antonio, and this guy wound up melting several wires, including wiring to the alternator. So, he offered to replace the wiring with new, for a fee of course, but at last minute he cancelled and still owes me the deposit. I have had nothing but bad luck with one unscrupulous mechanic after another. Anyhow, my question is two:
1. Anyone know a Mopar mechanic that does house calls in San Antonio?
2. Any suggestions for rewiring these burnt wires for my 71 Demon?

Thanks for the help.
 
At the risk of bein a smartass.....which I am not, I am being serious, unless you learn some automotive skills, you'll be forever at someone else's mercy. Get yourself a factory service manual for your car. Read it. Learn about it. They are simple beasts. If you were an electrician, you can wrench on a car. Just trust yourself and go for it.
 
If you have an electrical background you are already "one up." Several ways to go, buy a "repop" replacement "factory" like harness, and plug it in, or pull the old one out and attempt to fix it, or go find an good condition used one, in this day and age might be difficult

Or go aftermarket. There are many different harnesses "universal," and if you don't have much extra, like pumps, fans, EFI, etc, even a generic "12 circuit" can be made to work

You can download free shop manuals from MyMopar
 
RustyRatRod said:
At the risk of bein a smartass.....which I am not, I am being serious, unless you learn some automotive skills, you'll be forever at someone else's mercy. Get yourself a factory service manual for your car. Read it. Learn about it. They are simple beasts. If you were an electrician, you can wrench on a car. Just trust yourself and go for it.
Click to expand...
Since when did you quit being a smartass? It's one of your most endearing traits, Georgia.
 
Mymopar.com has the schematics, the tools are reasonably priced, and you have the basic knowledge to do the job. Go for it, and members here will help you out to no end. With my limited knowledge, I will, and I'm not alone.
 
67Dart273 has an extensive amount of knowledge on the wiring of our old beloved Mopars. Several other members, too. Some might be old and cranky, but their knowledge is invaluable. Crackedback comes to mind too.
 
Buy a new harness and have an auto/electric shop install it.
That lets you point the finger and possible repair cost at someone else if it doesn't work out.
no warranty when you do you own repairs.
 
Read this just to get an idea where some major problems lie. Then take a look and see if you see what's going on. Might be something you can handle with some Fabo advice. Nothing ventured nothing gained. Post#5 :thumbsup: He's our go to guy on this site. Helped me out before.
Good Luck.
Catalog
 
That infomercial has sent at least as many people down the path of electrical hell as its helped.
How 'bout we just give him the basics here.
Steve Mcbean said:
2. Any suggestions for rewiring these burnt wires for my 71 Demon?
Click to expand...
Depending on where they are, it may be worth while to either:
a) replace the entire harness.
b) replace part of the harness.
For something like the engine bay harness, M&H makes reproductions of decent quality - mostly sold through Year One.
For a partial harness, Evans Wiring might work with you.

This is a little bit like commercial wiring. The harness wrap is akin to the conduit - Circuits that don't relate can be in the same conduit.

Nice thing about automotive wiring is the circuits are generally color coded consistantly. Occassionally a color will be changed at a junction - and thats where the shop manual can be very helpful.

Here's the basics of how the car is wired.
There are two power sources: Battery, Alternator.
Power flows from whichever one can supply at the higher voltage. Battery is nominally 12.5 V, Alternator around 14 Volts when running.

Strip away all the other systems and just looking at the power feeds its something like this.
upload_2021-8-12_9-2-47.png

Notice the power feeds from the alternator and battery are joined at a welded splice.
Unlike a residential wiring, only some of the circuits are fed from the fusebox.

Also observe that all of the wires joined at the main splice are directly connected to the battery positive.
Think about what that means.
.
.
.
.
.
Exactly - always hot

This brings us to the Fusible Link.
The fusible link provides some protection if one of those main wires downstream of the battery is accidently grounded.
Chrysler used blue insulation for fusible links made with 16 ga wire.
So lets say there is a short to ground at the alternator's "batt" stud. Then the fusible link will melt. But lets say the feed to the headlight switch gets pinched against the hand brake bracket and grounds. Then its a tossup whether the fusible link will burn up before the headlight feed wire which was also often 16 ga.

The ammeter simply shows how much the battery is charging or discharging. Its roughly calibrate 40 amps to 40 amps.
Using this in combination with your handheld voltemeter can be very helpful in diagnotics.

Engine critical items are powered by the "ignition" circuit. This includes the alternator's rotor and any carburetor electrical devices (choke assist or idle stop solenoid if present). Pretty much everything else is viewed as an 'accessory'.

So these are the critical circuits needed to start and run the car.
upload_2021-8-12_9-31-13.png


Naming is usually:
A relates to Battery
R relates to Alternator
J1 Feeds Key switch
J2 is Ignition (Run)
Q1 is Accessary Feed - Always hot
Q2 is Accessory Feed - Switched
L is Lights
H is usually Horn

Wiring diagrams (and some harness diagrams) are in the service manuals.
You can download pdfs here
Service Manuals – MyMopar

This Master Tech booklet provides an overview of working with the Chrysler diagrams.
https://www.mymopar.com/downloads/mtsc/247.pdf
 
Last edited:
Steve Mcbean said:
Hi fellas. I havent been here in a while, since my car was in the shop for upgrades for 16 long *** months. I got the car back with nice upgrades, but also more problems than before. For one, there was a short somewhere under the dash and the car wouldnt start without wiggling group of wiring under the dash, so I called a mobile mechanic here in San Antonio, and this guy wound up melting several wires, including wiring to the alternator. So, he offered to replace the wiring with new, for a fee of course, but at last minute he cancelled and still owes me the deposit. I have had nothing but bad luck with one unscrupulous mechanic after another. Anyhow, my question is two:
1. Anyone know a Mopar mechanic that does house calls in San Antonio?
2. Any suggestions for rewiring these burnt wires for my 71 Demon?

Thanks for the help.
Click to expand...
Sorry to hear about your "adventures". These cars are now 50 years old and have had a lot of different hands in the pie. I bought mine back in November and found a lot of strange electrical issues. Replaced the under dash wiring harness which resolved a lot. When I pulled the instrument cluster I found someone had been in there and "made some things work". Had to replace the rallye circuit boards to fix that. Replaced switches, etc. All of this is pretty easily done by anyone with basic aptitude, but you already have an understanding of electrical principles. You may need to replace some harnesses like I did, but it will just take some bucko's and time to get it done. A big deal for my car was the under dash harness because it came with a new firewall electrical block. The old one was full of corroded & melted connectors. This will be a labor of love, so take your time, do your research, read the FSM, open your wallet and you'll be fine!
 
Just buy all of the harnesses new. They are easily installed, plug and play, expensive, but worth it. I have never regretted doing that, never. With 50 yrs of people hacking the hell out of the wiring and mother time, it's time to replace.
 
Yes, he may have to wait on some of the harnesses. Or, he can wiggle some more and burn his car to the ground.
 
Year one has a 25% sale right now. All harneses discount available except the dash, but they are plug and play.
 
73 Duster. Bought an under dash harness with bulkhead from Year one. Plug and play! That said, you will still want to bypass the ammeter gauge; discussed extensively here. Inspect your bulkhead connectors front and back as there is always a problem wire common to melting
 
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