Time to remove and repair, possibly replace, under dash harness

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hotrod swinger

hotrod swinger

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1973 Dart

I’ve been having electrical problems with my car from the day I bought it. Last year I had a parasitic draw and I discovered a section of wires behind the gauge cluster that were melted together. I repaired that section.

Tonight I was trying to diagnose a faulty temperature gauge and discovered another section of melted wires a few inches from the bulkhead.

I am going to pull the harness, hopefully repair it, if necessary replace it.

I think this will be pretty straightforward, any tips?

Thanks!
 
get yourself a few rolls of harness wire and lots of solder, terminals and shrink wrap. Pull the entire thing out and just start one wire at a time. Cut out old one, measure and cut a new one and graft in. Youll probably find there are 2 or 3 areas that are the problem and they can be "strung by" easily without messing with the terminated ends. The bulk wire doesnt even have to be 12 different colors, just get an assortment of colored small zip ties in different colors (variety tube from HF) and put a different tie or 2 on each wire where they run parallel to each other. They may all be black or red or green (Id recommend at least 2 colors of wire to start) but youll know where they all go by matching up the zip tie colors. AWM or SXL wire is auto grade. there are a few that need to be larger guage but most can be like 14.
 
Buy a new harness from Yearone produced by M&H. Wait for a 30% off sale.

Sounds like you were lucky catching it twice, don’t wait for strike three.
 
If it's that bad, replace it. I bet the bulkhead connectors are welded together and messed up too. You'll spend days chasing it all and may still miss something. Plus most repairs just aren't as good as virgin harness.
Pack all connections with grease.
Look into bypassing the bulkhead and all that stuff
 
If you can solder, and get a couple of crimpers you can rebuild it. It is a fair amount of work. Having a bench large enough to "stake" it down and stretch it out with nails helps A LOT. Lay it out, tie it and nail it down, and temporarily tape/ tie off each branch and strip the wrappings off.

You can buy most of the terminals.

It really just depends on how much money you have vs how much time and skill you have
 
i just put new forward harnesses in from year one. they were awesome. I also just replaced my under dash harness with a really nice used one from a fellow member. it also went in really nice and after I was done everything worked. it took 3-4 weekends but was worth it.
 
you have 49 year old wires in a car that Chrysler designed to last 5-10 years. I'd go with M&H - a good investment
 
Do it yourself, or pay Yearone? That's the question. I'm redoing mine. I'm in Ontario and an underdash harness would have been close to $1000 delivered.
 
I enjoy soldering and I like a challenge, so I think I will remove it and examine it and make a decision.

Most of the connectors are in good shape, none of them are melted, including the bulkhead. Maybe I’ll just have to solder in a couple new sections and repair some areas with shrink tube.

I think it will depend on what I find in there.
 
4spdragtop said:
Do it yourself, or pay Yearone? That's the question. I'm redoing mine. I'm in Ontario and an underdash harness would have been close to $1000 delivered.
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I used to pu em from the local Boneyard, but that was Many Moons Ago... that being said, when YOU rebuild something, YOU KNOW what You Have...for instance, an Engine harness.. if Ya happen to be on that dark long lonely road one night, Ya WILL have a slightly better time doing a Roadside ( not that You should have too) than just a plug and play unit. I Agree with everyone here on fact that, it is a time and money thing. Then again, I hand bent and double flared all the hard lines on my 66 Sat... back when I had patience! 20 bucks + fittings. ...
 
If you have the time and don't mind putting the car down and you have the skills, I say either build a new harness yourself, or repair yours. I do also agree that those wires weren't really made to last 50 plus years, especially with the plastic compounds of yesteryear making up the insulation. It gets hard and brittle, unlike modern compounds that last much, much longer. So there's that to consider, too. I think what I might do if it comes down to a harness replacement in Vixen is look at a new universal harness from somewhere like Speedway Motors. Sometimes they run really good sales. I actually have a universal 21 circuit harness I got on sale for my rat rod truck for 89 bucks. It was normally 299. I was in such disbelief, that I was looking in my email everyday for the cancellation on my order, but amazingly, it was here in a few days. Very complete with switches and all. GM colors of course, but who gives a ****? I sure don't.
 
hotrod swinger said:
I am going to pull the harness, hopefully repair it, if necessary replace it.

I think this will be pretty straightforward, any tips?
Click to expand...
With a more major repair - which yours is, laying it out on a plywood board may be a big help.
Some examples here: WIRING NIGHTMARE

hotrod swinger said:
I enjoy soldering and I like a challenge, so I think I will remove it and examine it and make a decision.
Click to expand...
Good plan
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hotrod swinger said:
Most of the connectors are in good shape, none of them are melted, including the bulkhead. Maybe I’ll just have to solder in a couple new sections and repair some areas with shrink tube.
Click to expand...
Mmmm,
With that melting you may find it better and easier to replace the entire section of wire from juntion to junction.
Crimping the open barrel connectors on the bench is not difficult.
For splices you can order the open barrel splice connectors and use with or without solder. I don't usually solder them for use inside expecially If the wire needs flexibility in that location.
For heat shrink tubing, get several sizes in types that flexible and types that are fuel resistant (for engine compartment).

There are several good threads on crimpers, connectors and terminals. I think you've seen them or links to them.
The only terminals that can not be easily replicated are the ones that had molded rubber insulators and seals.
 
hotrod swinger said:
I’d like to know why my fusible link didn’t protect that circuit.
Click to expand...
The link is just a specially insulated 16 ga wire.
It takes a lot of current to melt that link. Put a 100 amps through it and it will probably go poof in a second. The feed wire to the key switch pinched in column would be an example of a short that would almost certainly do that. Another would be taking a pair of pliers under the dash and contacting an ammeter post and body sheet metal. Or a wrench shorting the alternator batt post to the alternator bracket.

However that 16 ga wire can carry 30 or 40 amps without melting. But subjecting that wire to 40 amps will cause heat. The longer that amount of current tries to flow through, the hotter it gets. Really nothing in that circuit is really intended to tolerate 40 amps for long periods of time. The same goes for the alternator output wire, although it occassionally does need to handle up to 30 amps or so. (driving at night with heater and wipers going).

Once you have the harnesses out you can make a better diagnoses. But you may never know for sure. There could have been an intermittant short on an unfused wire, or the previous owner may have used the alternator to recharge a heavily drained battery, or ????

upload_2022-1-14_11-20-50-png-png.png
 
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RustyRatRod said:
If you have the time and don't mind putting the car down and you have the skills, I say either build a new harness yourself, or repair yours. I do also agree that those wires weren't really made to last 50 plus years, especially with the plastic compounds of yesteryear making up the insulation. It gets hard and brittle, unlike modern compounds that last much, much longer. So there's that to consider, too. I think what I might do if it comes down to a harness replacement in Vixen is look at a new universal harness from somewhere like Speedway Motors. Sometimes they run really good sales. I actually have a universal 21 circuit harness I got on sale for my rat rod truck for 89 bucks. It was normally 299. I was in such disbelief, that I was looking in my email everyday for the cancellation on my order, but amazingly, it was here in a few days. Very complete with switches and all. GM colors of course, but who gives a ****? I sure don't.
Click to expand...
I paid $85 on the Speedmaster black Friday sale and was thinking this is gonna be junk and low and behold it's been working great...
 
I started peeling the wires apart from the bulkhead back. Not looking good.

All of the ignition wires and the main charging circuit were melted together.

I’ll take a closer look tonight, but it’s looking like a pretty serious repair job.

894934AF-BF1E-44BA-BD97-4C6E36D017D6.jpeg
 
Where can I buy the terminals for the bulkhead connector?

Im in British Columbia.
 
The bulkhead connector looks surprisingly good, no melting, would it be foolish to just splice wires and keep those terminals or should I install new ones? Have no idea where to buy them.
 
DON'T DO IT !!!!
Those terminals are usually the ultimate source of the over heated wires - corrosion between the two parts of the terminals. Taking the bulkhead connector apart is pretty easy and it's as much work to do the splice as to put on a new terminal. Pack the bulkhead connector with dielectric grease when you get ready to put it all back together.

I would especially suggest to you that you get a new underhood harness (everything from the firewall forward) even if you decide to rebuild the underdash harness yourself. Think about it - the dash harness is inside your car and away from extreme heat, where the wiring under your hood is outside and in an enclosed space with your engine and exhaust.
 
I have a new under hood harness, a jumper from the alternator to battery, and headlight relays.
 
The connections honestly aren’t that bad. That was the one part of that section that wasn’t melted. The wires were fine from about 6 inches out from the bulkhead. The connecters actually look good. I can pull them apart and clean them? Possibly re-solder them?
 
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hotrod swinger said:
Where can I buy the terminals for the bulkhead connector?
Im in British Columbia.
Click to expand...
Most likely will have to mail order. Some sizes may be available at an automotive store or a big electronics store.
Sources for Chrysler type wire terminals

hotrod swinger said:
a jumper from the alternator to battery,
Click to expand...
There's another possible explaination why the fusible link didn't go first.

hotrod swinger said:
The connections honestly aren’t that bad. That was the one part of that section that wasn’t melted. The wires were fine from about 6 inches out from the bulkhead. The connecters actually look good. I can pull them apart and clean them? Possibly re-solder them?
Click to expand...
They were never soldered. They are all crimped.
Using open Barrel Crimpers: A bit of Wiring 101
also a discussion on Lets Talk Open Barrel Crimpers - Reviews and Discussion

There's also a pretty good search engine here.
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I'll recommend these two:
1969 Dodge Dart - Engine Compartment Main Bulkhead Connector

Cleaning bulkhead connectors

and for splices.
Inline wiring splice clips........from the Dodge RAM service manual

I think wire is covered in the Chrysler Connector thread.
Under the dash, automotive primary is fine.
For hot, fuel, oil or salt and moisture, marine grade or SAE TXL, SXL or GXL should be considered.
Marine supply often have a wide variety of insulation colors and will sell by the foot. or maybe in BC by the decimeter.
Rhode Island Wire has a lots of insulation options.
 
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