Harness Wire Splices - Solder or Crimp ?

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23yrRebuild
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Harness Wire Splices - Solder or Crimp ?

Post by 23yrRebuild »

Hey all,
I'm in the process of troubleshooting some electrical gremlins in my wiring harnesses, that I suspect may be caused by some faulty OEM splices. I would like to repair, or replace those splice connections by either soldering, or crimping butt splice connectors, or some other method I'm not aware of. Does any anyone have any advice or recommendations, please ?
Mike
Last edited by 23yrRebuild on Fri Feb 19, 2021 9:56 am, edited 1 time in total.
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Re: Hareness Wire Splices - Solder or Crimp ?

Post by Habitat.pat »

Crimp vs solder is a religious question. I’ve done both over the years.

These days correctly done crimp are the most reliable. Go with the uninsulated splices then cover them. Use a quality crimper.

I won’t use insulated connectors in any place where reliability is required & only where they are exposed.

In the 60s I went through a 3 week soldering course. We learned high reliability soldering similar to what NASA was using. By today’s standards it was the dark ages. Reliable soldering works well when there is no vibration, not in vehicles.

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Re: Harness Wire Splices - Solder or Crimp ?

Post by 23yrRebuild »

Hi Pat,
I've heard and read the same information regarding the mechanical and vibrational reliability of soldered connections. And I'm inclined to agree that crimping would be preferred to use in our cars. Specifically, I was looking at how the factory connected a second wire into the middle of another single, longer wire, by what appears to be some type of crimped barrel and "wire biting" connector. Looking at the ground wires in the schematics, as well as the other splice locations, it seems to me, that it would be better to crimp one wire run into one end of a butt splice sleeve, and then crimp another main run wire and a second "branched" wire on the other end of the sleeve, then heat shrinked and taped. Would that be the idea, then?
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Re: Harness Wire Splices - Solder or Crimp ?

Post by Habitat.pat »

Sounds like the best method we can do. The original taps were a piece of metal wrapped around the main wire & tap wire, then soldered. I’d suggest bringing the wire you are going to cut out of the harness & putting the splice where it can be gotten to down the road.

I just finished replacing my entire wiring harness I got rid of as many connectors as possible. I built a single bumper to bumper harness. All taps are outside the harness so they can be gotten to easily if needed.

I mainly used terminals from Vintage Connectors. Only problem was that their connectors are sized for 16ga. wire so for the 18ga. wire used for some circuits required me to double over the wire in the crimp. 14 ga. worked with their connectors but I had to go to different terminals for the 12ga. Headlight circuits.

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Re: Harness Wire Splices - Solder or Crimp ?

Post by Gregs672000 »

I'm certainly no expert when it comes to electrical. However, I just did a bunch for the EFI and was very happy with the crimp connectors that have the shrink tubing shield around them. I shrunk them with a torch lighter (easy) and they melt/seal themselves to the wire and make a much stronger connection. They are stupid expensive at auto parts stores for the cost per piece so I suggest Amazon or Ebay (1/4 the cost). They make a variety which includes connectors designed to permanently splice in longer pieces of wiring.
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Re: Harness Wire Splices - Solder or Crimp ?

Post by cbez »

you can do both if you want. crimp, little bit of solder, self seal heat shrink on top. a properly done crimp is a great connection. a crappy crimp over a crappy pre insulated terminal is garbage.
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Re: Harness Wire Splices - Solder or Crimp ?

Post by Habitat.pat »

The main problem with soldering is that it makes the relatively flexible stranded wire a solid wire which breaks much easier. The NASA method was to use a special pair of anti-wicking tweezers that acted as a heat sink to keep the solder from flowing out too far. At that time soldered electric connections were more reliable than crimping.
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Re: Harness Wire Splices - Solder or Crimp ?

Post by todd lorber »

We can wait for Curtis to chime in, but I'm a fan of soldering when two WIRES are to be connected (wrapped in double heat shrink). At the ends, an automotive electrician recommended a proper crimp, with a "dab" of solder drawn into the crimp afterward. Then heat shrink where possible. Sometimes you cant fit heat shrink into the plastic connector so you have to forgo it there.

I did frame/motor swap on my 54 pickup and put in an '05 fuel injected motor using stock brain and wiring harness. I cut and spliced at least 60 wires via the method above and to my surprise the truck started and has run flawlessly for the past 4 years. All sensors, ignitors and feedback systems etc. have been perfect.
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Re: Harness Wire Splices - Solder or Crimp ?

Post by GoldHawg »

Crimp then solder; at least this is what MAD Enterprises always promotes. I'm following this approach in my wiring
http://www.madelectrical.com/electrical ... ges2.shtml
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Re: Harness Wire Splices - Solder or Crimp ?

Post by TurboRagtop »

I’m in the camp of using non-insulated, tinned, copper terminals and high quality crimping tools. Not the auto parts store grade crimpers! Solder according to your religious convictions.
Then seal with adhesive lined shrink tubing. Stay far away from the evil insulated connectors as you can never really inspect and verify the crimp after the fact.
What’s worse is the insulated connectors allow moisture and air into the connection, which the adhesive seal-type shrink tubing resists. Gas-tight connections folks! That’s what works best.
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Re: Harness Wire Splices - Solder or Crimp ?

Post by Curtis »

Yes, I have read on the merits of solder vs. mechanical crimp connections and still the water is muddy. My question would be when it gets to the terminal it's solid anyway so why is the solder considered so substandard for electron flow?

Let's start with original Datsun harnesses. They spliced wires using a splice terminal and sometimes they soldered them and sometimes not. Then they just taped over them. The large wires for the ammeter, alternator and ignition switch they just wrapped one wire around the other and soldered and taped. Large wires that end in a terminal are all soldered. Splices of small wires might have 3 or 4 wires together.

The place that I buy most of my wire from makes harnesses for all kinds of classic cars. I asked what they do and they said they solder everything. The reason being that they don't have the industrial type crimper used to make the original harnesses and do not want anything coming apart or failing.

I use a combination of crimping and soldering with splices. I looked a long time to see what the auto industry now does and just couldn't come up with anything better. Another thing to remember is now with so much computer control they use wire looms of much smaller wires.

I like to seal the joint or splice with just a touch of solder if I can. Seriously, if the wire gets a little more solder than you want so what. The places where the splices are for the most part are not going to be moving around and get constant flexing. If I think the crimp will be fine then I don't solder. In most cases I then cover it with a double layer of heat shrink. It's what I did/do for my wiring and it has worked great. If you see what I build I don't muck around with poor quality, I overbuild.

The experts I think will continue to debate this and I'm not one of them.
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Re: Harness Wire Splices - Solder or Crimp ?

Post by Habitat.pat »

Curtis:
My question would be when it gets to the terminal it's solid anyway so why is the solder considered so substandard for electron flow?

As I understand it the solder doesn’t impede electron flow, it just makes for what I think of as a an extended lever that exerts extra stress on the now rigid wire where it joins the terminal. Without solder you have multiple smaller wires which, when flexed are less likely to be affected.

As I said in my first post, it is a religious question & in the end it probably doesn’t make enough difference.

It may come down to something other than reliability, such as reproducibility or speed or cost. Once the bean counters get involved all bets are off.
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Re: Harness Wire Splices - Solder or Crimp ?

Post by Curtis »

I thought I read something about the electrons traveling on the outside of the wire concerning the solder vs. crimped, but then again maybe not. JT is an electrical engineer, ask him.
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Re: Harness Wire Splices - Solder or Crimp ?

Post by Habitat.pat »

The skin effect on wire is an A.C. thing. I’d have to check but I remember seeing the same kind of religious discussions about whether it had any effect on speaker cables. RF frequencies is where it really comes in to play.

JT68, would you please give us a Jethro Bodine short course?

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Re: Harness Wire Splices - Solder or Crimp ?

Post by cbez »

if you have the right amount of solder in the connection it is not going to stress the wire. you aren't supposed to run it up the wire. like Curtis said you generally shouldn't have much movement there anyway.

electron flow and whatever is just getting too pedantic. I was taught they move on the outside surface of the wire, but it doesn't matter, they are 35 amp cars. any soldered terminal is going to have way more than enough capacity.