Replacing Wire Harness VS Repairing Damaged Areas

[Black and Blown]

I've had the luxury of not having to deal with any wiring issues for the past 22 years of owning a 1970 Charger.  Well, my day has come - lucky me! 

So I'm trying to educate myself by reading old posts and using the search feature.  I've learned a fair amount, but have a couple questions I'm hoping some of you may chime in on. 

All the wiring has worked as it should the past 22 years.  Every now and then (but rarely) I'd get a "burning wire" smell.  The most recent instance occurred at the end of last summer.  Shortly after the smell, I arrived at my destination and shut the ignition off.  But the engine continued to run.  I turned the key back on and off a few times - nothing.  Still running.  (This car has Holley EFI).  So I drove it home and disconnected the battery, where it sat until last week.

I've been asking around here in Sioux Falls SD for someone who knows the ins and outs of old Mopar wiring.  Sadly, I just haven't found anyone.  But I did get a recommendation from the shop where we take our modern vehicles, so I had a conversation with this particular mechanic and felt good enough to bring the car in to him.  He's got the dash out and the firewall connectors undone.  There is damage to one of the prongs and surrounding plastic on the firewall under the hood.  He also found a short in the parking brake socket.

How does one go about making the decision of what to replace?  I'm new to this - can I buy parts to replace the firewall connections and a new under-hood harness to replace the damaged one?  And if so, what company sells reliable stuff?  Or is there some reason I should replace additional harnesses? 

I sure would appreciate some advice from those of you who have been down this road.  Thanks so much!   

[Nacho-RT74]

My opinion... and based on my own experience.

Engine bay harness worths to be replaced. The environment is too wild so any partial fix will take to another extra partial fix later.

Interior harnesses... mmm they usually get damaged at very tipical and focused spots, ammeter wires at bulkhead and if a heavy damaged, some wires around. Sometimes ign switch wires. These are easy to fix and it could take to some good definitive upgrades which in any case with a new one is better also to get it upgraded.

Plus, an underdash harness price spins around $500-600... while a refresh or fix on them probably won't take more than $60-80.

If bulkhead gets damaged, is replaceable or serviceable.

Sure I have some skills to proceed with my suggestion.

[b5blue]

  For 70's up a big issue is the white connector to the ignition switch in the column. Look to see if the big red wire in the white connector is burnt. The metal connectors inside are not heavy enough to carry much load. On that note I've had 2 replacement switches fail inside the column, they quit cranking the starter. I've put a splice at the connector on my new harness and now use a starter button switch that works just the starter wire at the solenoid. 
  I cleaned connectors using salt and vinegar mix and repaired my harness using "Alumicon" connectors you can get at Lowes. I also use a Denso 120amp Alt. but there are much better alts now.
  Later I replaced ALL wire harness using a Black Friday Sale at Year One. They have an exclusive M&H contract. I'll post some links next.

[b5blue]

These can carry large loads safely https://www.lowes.com/pd/Alumiconn-2-Port-Al-Cu-Wire-Connector-10-Pack/5000926655
This is a upgraded Alt  https://www.qualitypowerauto.com/pages/ChryslerMegaAmp.php

[b5blue]

To reduce the load on the ignition switch and under dash wiring I've installed 40amp control relays for several things like ignition fans and such. I know nothing about the needs of fuel injection and can't imagine why the car didn't turn off. 

[b5blue]

  30 years ago when I first bought my 70 the only fix I couldn't do was charging. As I used the car as my primary night time added headlights and wipers if raining. The lazy ALT output at idle would have my ALT gauge swing back and forth telling me I was drawing off the battery then when amps climbed off idle RPM's the system would try to recharge the battery's missing load while feeding demand.
  This seesawing heats up the wires in stop and go driving and the fix is having enough ALT output at idle. To this end the factory made a "Fleet Upgrade" that runs an additional wire from the ALT to the main splice near the ALT gauge. Your melts will tell you your weak points but not how to stop the problem.

[b5blue]

This sight has great helpful info for anything car type electrical. https://www.bcae1.com/

[Black and Blown]

My opinion... and based on my own experience.

Engine bay harness worths to be replaced. The environment is too wild so any partial fix will take to another extra partial fix later.

Interior harnesses... mmm they usually get damaged at very tipical and focused spots, ammeter wires at bulkhead and if a heavy damaged, some wires around. Sometimes ign switch wires. These are easy to fix and it could take to some good definitive upgrades which in any case with a new one is better also to get it upgraded.

Plus, an underdash harness price spins around $500-600... while a refresh or fix on them probably won't take more than $60-80.

If bulkhead gets damaged, is replaceable or serviceable.

Sure I have some skills to proceed with my suggestion.

Thank you for this input.  It's very helpful.  Is there a particular harness supplier you would buy from?  I see the next comment suggests Year One as their choice.

[Black and Blown]

For 70's up a big issue is the white connector to the ignition switch in the column. Look to see if the big red wire in the white connector is burnt. The metal connectors inside are not heavy enough to carry much load. On that note I've had 2 replacement switches fail inside the column, they quit cranking the starter. I've put a splice at the connector on my new harness and now use a starter button switch that works just the starter wire at the solenoid. 
  I cleaned connectors using salt and vinegar mix and repaired my harness using "Alumicon" connectors you can get at Lowes. I also use a Denso 120amp Alt. but there are much better alts now.
  Later I replaced ALL wire harness using a Black Friday Sale at Year One. They have an exclusive M&H contract. I'll post some links next.

Thanks for the helpful tips! 

[metallicareload99]

I agree with the above, in my 20+ years of driving around my Charger I've had similar experiences. Aside from self inflicted problems, the bulkhead connector and high current through OEM switches are the main issues

How much are you willing to modify the factory wiring? It sounds like the damage to your dash wiring is relatively light. If so I would repair that, and IF you were willing, make some modifications. The under hood harness don't seem to last forever in their relatively harsh environment. That's really the only one I would consider replacing. Otherwise, how bad is the damage? If not severe then it could be repaired and modified to reduce the likelihood of future problems

First, bypassing the heavy charging wires that pass through the bulkhead connector.

Next, any accessories that need a lot of electricity I would supply them through relays, the closer to the alternator the better

[Black and Blown]

I agree with the above, in my 20+ years of driving around my Charger I've had similar experiences. Aside from self inflicted problems, the bulkhead connector and high current through OEM switches are the main issues

How much are you willing to modify the factory wiring? It sounds like the damage to your dash wiring is relatively light. If so I would repair that, and IF you were willing, make some modifications. The under hood harness don't seem to last forever in their relatively harsh environment. That's really the only one I would consider replacing. Otherwise, how bad is the damage? If not severe then it could be repaired and modified to reduce the likelihood of future problems

First, bypassing the heavy charging wires that pass through the bulkhead connector.

Next, any accessories that need a lot of electricity I would supply them through relays, the closer to the alternator the better

Thanks - do you know who sells the 3 engine compartment harnesses without the dash harness?  I like that idea of repairing what we can.

[metallicareload99]

Only one of the three is the engine harness. I got mine from Evans Wiring, not sure if they are still open as it was a long time ago. They have been great to deal with and make a nice harness

evanswiring.com

[b5blue]

https://www.yearone.com/Product/chrysler-b-body/hu107b

[b5blue]

Remember you fixing 55 year old wire that's been subjected to less than ideal conditions. 

[b5blue]

  Evens is/was good but after doing a new harness "tug test" (Pull on the connector's wire connection.) one wire just slipped off the connector. Check every aspect of any new harness to be certain it's made proper. (I made harnesses in the USAF for transmitters.)

[Derwud]

Replace it all, do you have to do it all now, no, but it will make you time driving the car a little less stressful.
On my Wagon, I rewired the Engine Compartment and the used an American Autowire Universal kit for under the Dash.. It works AWESOME...

[Nacho-RT74]

Originals works awesome too. And after 50 year being abused still works awesome LOL. Just need to be refresh it at certain points. Cheaper and easy to do

[Kern Dog]

I'll bet that the weather/climate in your area determine the lasting integrity of your harness.
Out here on the West coast, cars don't usually rust that bad. Corrosion of wiring seems to be less that in colder climates too. I have original interior harnesses in 5 running, driving classics in years from 1967 to 1975. I've done ammeter bypasses on 4 of the 5 though.