Evaluating old Wiring Harness

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Miranthis

Miranthis

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I am disassembling my 66 Barracuda for a restoration and have the harnesses out. I cannot separate the engine side from the terminal block, mainly because terminal B (black wire to the Batt side of the ALT and inside to the black terminal of the ammeter) is, well, melted. (first pic is top of the bulkhead conn. showing melt through and second is of the melted and then corroded black wire to the alternator)

Also the connector to the light switch is also melted, it looks like around the H terminal the outputs to the Headlights through the floor switch. (3rd pic)

Assume that old, corroded wiring heated up and did this on the higher amp draws. New replacement wiring harnesses (with new connectors nad bulkhead block) should fix this as new wires will be lower resistance than the old corroded ones, correct?

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I was in a similar situation with my car, with melting and crumbling connectors. Replaced with new harnesses and also added an additional charge wire to share the load with the bulkhead. Wiring stays cool to the touch all the time.
 
Be sure to use dielectric grease on the connections when you install the new harness. Corrosion in connections like the bulkhead connector that tends to go many decades without ever being taken apart will build up oxidation and resistance leading to heat. I would bet that is what melted the engine side connector in your case. I literally pack the bulkhead connector in the dash harness before installing it.
 
If you want to salvage what you have and make an original harness work, put the word out. I'm sure there are members here that have stuff that can help you out.
 
@Miranthis I had a similar situation with my Dart when I first bought it. The previous owner had shoved a screw into the bulkhead connector on the main power feed. My buddy saw it, laughed and took it out. When I went to start it, nothing. So we rode with the screw for a while. That hole in the top of your's reminds me of that.

Year One carries this one and also a version if you're running a Mopar electronic ignition box. It is a good quality piece and everything is well marked. Pricey? Yes, but so is being stranded out of town late at night.

https://www.yearone.com/Product/chrysler-a-body/hu270a

When I swapped engines, I went with a new under hood harness and never looked back. It wasn't cheap but it's good insurance. If you need any help, I'm over in Lee's Summit, but work in Merriam. Give me a shout.
 
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@RAT ROD AL has an engine bay one listed right now.
I may have went overkill, but our 67 original harness LOOKED great, but very stiff and insulation cracking in a few spots. I did a complete rewire including the dash back.
 
You could put harness on plywood or pegboard. Unwrap and change out 1 wire at a time. Rewrap and install. Stole pic from web, but something like this.
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Just buy your harnesses new, unless you have the quirk of trying to repair the junk you have or have the skills to do the painful make your own harnesses. Yes, they cost a lot, but they are plug and play easy, move on.
 
I will be replacing it with new, but wondered if i needed to increase the gauge of the high amp wires. Sounds like not if i go new. I am curious about the new harnesses as i know there are differences between the various models and options. I dont need any AC wiring and have manual trans so the reverse light switch is wired with a separate harness.... some of the harnesses dont ask enough questions, so wonder if its just one new harness with everything (one size fits all) and not truely one that replicates stock (several options, sub harnesses, and such).
 
You don't need to change the ampacities of any of the wires whether they are old or new unless you change something that requires a higher amp load. The engineers at Mopar had that pretty well covered in 1966. Age and failure to maintain these old harnesses by the owners is generally what causes their failures. It's really no different than having a P.M. on your main battery cables. Corrosion gets in everywhere. If you don't occasionally clean the alternator terminals, ballast resistor, bulkhead, etc... and especially ground connections the corrosion creates higher resistance and greater load which can destroy even properly sized wire, terminals and connectors. I have personally never had to change to a new harness, but I have heard wonderful stories of ordering aftermarket ones and horror stories about how wrong they were. Best of luck with whatever you decide. The one year only 1966 Barracuda is a true gem especially as it looks like you have the commando 273 4 gear version. Karrrin and I have a Citron Green 66 commando 273 4 gear formula s car saved in our barn to restore when we retire. (if ever)
 
Personally, I would call Jamie at Mega Parts, he is less expensive than Year One, same M& H harness, even on sale, PM me as to why, not saying here on this thread. Or, call Evans wiring. Both are top notch. Remember, most harnesses on Mopars are individual. Wiper, trans, engine, dash, tail light, etc. Some 3 or variable speed wipers have the harness attached. On the three cars that I own, 2 had complete wire replacement, hacked and brittle insulation. One was excellent except for firewall forward, cracked insulation. Use dielectric grease to protect all connections. The last sentence is just what I do.
 
jeff alder said:
You don't need to change the ampacities of any of the wires whether they are old or new unless you change something that requires a higher amp load. The engineers at Mopar had that pretty well covered in 1966. Age and failure to maintain these old harnesses by the owners is generally what causes their failures. It's really no different than having a P.M. on your main battery cables. Corrosion gets in everywhere. If you don't occasionally clean the alternator terminals, ballast resistor, bulkhead, etc... and especially ground connections the corrosion creates higher resistance and greater load which can destroy even properly sized wire, terminals and connectors. I have personally never had to change to a new harness, but I have heard wonderful stories of ordering aftermarket ones and horror stories about how wrong they were. Best of luck with whatever you decide. The one year only 1966 Barracuda is a true gem especially as it looks like you have the commando 273 4 gear version. Karrrin and I have a Citron Green 66 commando 273 4 gear formula s car saved in our barn to restore when we retire. (if ever)
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At one time this car had a lucas driving light that may have increased the h/l load. Several of my mopars over the years have had the ammeter fry and get bypassed (not this one, but 'only just' by the looks of it). This one did burn through voltage regulators on the regular, however, also no shock in light of the wiring.

Finally, this one ran w/o an engine ground strap for a little while, on accident, after the intake was pulled and gaskets replaced.... finally figured that out when the lead swage on the throttle cable that was acting as the ground, melted one night with the high beams on... i saw the red hot pinpoint under the dash and smelled it.

I am sure all of that contributed to the general condition of the harness. My resto guy made me promise to buy/use all new wiring before he would agree to do my car...i was doing it anyway, but it was good advice.
 
I have a new M&H '66 Barracuda forward engine/light harness with the Mopar electronic ignition mod. If you plan on going that route, contact me.
 
As said you might make changes like headlight relay (highly recommended) and ignition mods. Electric fuel pump, Electric fans, higher amp alternator, bypassing Amp gauge and going voltmeter. Now is the time to consider any upgrades as well. Using a higher amp alternator will require some wiring upgrades. JMO
 
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