Automotive electrical connector tech: TOD

I HATE wiring but it's really not that bad if you take it one thing at a time.

I didn't find that we had one of these thresds but with how much crimping and soldering and such I've been doing on my Buick, I have gained a bit of knowledge. I'm not the biggest fan of soldered connections on a car, especially one that vibrates due to 600+ ft lbs running through it. Small connections I'm fine with but my soldering skills are amateurish. That brings me to crimp connectors.



Not my picture as this image has AC, but I've traced some intermittent issues I'm having to this connection with the help of my Electrical Engineer brother-in-law yesterday. Believe it or not, that's OEM connection on '68-72 Skylarks (other A-body's as well I'm sure) that's been crimped and soldered. My wires have fatigued just outside the soldered connection. I believe I've seen that on the "squarebody" GM trucks as well. So that mean's in my '89 Suburban harness in my Jeep as well. In the case of my car, that connection has lasted 52 years so it's not a horrible idea despite how it looks. I'd also say that the harness in my car has been a bit "molested". That's likely the correct term.

My question/thought is that I believe these connections with heat shrink over the top will be the modern equivalent? Those are about 10 gauge wire, possibly 8 gauge and when combined the yellow butt connector isn't quite the right friend.






For my case, I think I'm just going to buy a new engine harness for this old dawg. I think the butt connector/heat shrink will cover for me in the interim?


Would any folks here have a better solution for such a repair and if so, please share with the class below. Also if you have other tips/tricks/issues maybe this thread can serve as a "go to" library for electrical faux paus/repair?

I've done a ton of soldering on a 12 pin wire harnesses at work, unfortunately... I've become pretty good after several repairs where the harness bends repeatedly and wires break. I've cut in new harnesses several times now and it's a tedious PITA.

IMO soldering is the most reliable option, a good soldering iron makes a massive difference. I bought a cordless Milwaukee soldering iron, which has been amazing. Milwaukee Cordless Soldering Iron

A 2nd option are the heat shrink connectors with solder in them. I believe they're weather resistant, pretty simple and easy to use. Heat shrink soldering connectors

Lastly, if you're just going to use crimp connectors I'd highly suggest a pair of crimp pliers that actually dent/crush the barrel inside the connectors for a reliable connection. Crimping Pliers

I've gone back and forth on soldering connections. My first stereo install was with wire nuts, and that was dumb. I graduated to crimp butt connections, which are easy and so I just did that for a while. Then I started worrying about doing it "right" and started soldering the old fashioned way, which is frankly a bit of a pain when you're under the dash and not at the bench. Then I heard about fatigued solder connections, and then I took apart a 4Runner harness and all the OEM connections were crimped, so I went back to that. Then I found solder/heat shrink connectors and that's my current go-to. They support the wires in and out of the connection so they're less likely to fatigue, and there's no way moisture is getting in. They're super easy with a little butane heat gun.

This "Sopoby" is the brand I've been using for a couple years now, no complaints yet: https://www.amazon.com/Connectors-Sopoby-Waterproof-Electrical-Automotive/dp/B0BKSJQC9Q

Greg said:

I've done a ton of soldering on a 12 pin wire harnesses at work, unfortunately... I've become pretty good after several repairs where the harness bends repeatedly and wires break. I've cut in new harnesses several times now and it's a tedious PITA.

IMO soldering is the most reliable option, a good soldering iron makes a massive difference. I have a cordless Milwaukee soldering gun which has been amazing. Milwaukee Cordless Soldering Iron

A 2nd option are the heat shrink connectors with solder in them. I believe they're weather resistant, pretty simple and easy to use. Heat shrink soldering connectors

Lastly, if you're just going to use crimp connectors I'd highly suggest a pair of crimp pliers that actually dent/crush the barrel inside the connectors for a reliable connection. Crimping Pliers

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Excellent points @Greg . I would assume a rail application gets a LOT of vibration that might only be duplicated by an off road vehicle that sees a lot of use?

I also strongly agree to use a quality set of crimpers and crimp terminals if youre going to use crimp connections. I did buy a few electrical things this morning that I now feel are essential in my garage.

-klein clamp meter multi meter

-quality soldering iron as Greg mentions above
-these looked kind of handy and would have had value yesterday






@Kevin B. , i have not loved those butt connectors but I'm using a heat gun to try to melt the solder. I'll possibly bounce back to a butane and give them a try again

I have never had a problem with a solder splice and heat shrink but I guess I can see that causing an issue with fatigue down the road.
I have set up for and use a lot Duetch plug type connectors everywhere a plug and socket belongs. I think it's a much better and watertight connection than weatherpak.

Having been in the Wire Harness industry for over 27 years, I cannot overstress the importance of using the proper crimp tooling. Contact manufactures will identify the proper tooling, this is typically their own tooling. If you cannot get the manufacture's tooling, you should use aftermarket tooling that produces the same crimp.

I put together some information for my son, others may find it interesting, see attached.

Mercedes Benz tech bulletins specifically states electrical repairs on damaged wires are to be done via crimp terminal only, as solder joints can cause the wire to become work hardened, and therefore a stress break point.

I am a huge fan of the crimp connectors with built on heat shrink, so much easier than using shrink tubing with it separately. I got a cheap kit on Amazon a while back, and the special crimp tool works great.

I finally took the plunge and bought a whole bunch of bulk wiring supplies. I feel like if you have all the proper stuff on the shelf you will always do it right. For permanent wire connections I stick with either lugs or Duetch connectors.

Can we talk about Deutsch vs Weatherpak? I'm ready to throw out all my cheap knockoff connectors, but I don't know enough to know what to replace them with.

As far as soldering, YouTube helped me quite a bit with mine.

Crimped connections can be great, but really good crimping tools/supplies are way more great. Your dad’s cheap-ass stamped 12 gauge crimpers just damage the heat shrink on shrinking butt connectors.

What would be a "quality soldering iron"? @Greg mentioned the Milwaukee unit. Thoughts on this "name brand"? I didn't catch the brand of my brother-in-law's soldering iron but it didn't suck near as bad as my $8 unit from 20whatever years ago.





I like the temperature readout, the holder dealio, the flux and brass wool gadget and such. I'm sure I'd get what I paid for and this isn't really any better than my $8, 20 year old soldering iron. Although it's probably light years better? Are there good brands to buy? Just buck up and get the Milwaukee unit for $200?


I have yellow tools. For no other reason than Great Basin Supply or whatever was selling them in Moab one year.

....hah!!!! That's not even a DeWalt. I did the same thing on a heat gun. While the heat gun works, it's not that impressive. I don't see an actual DeWalt unit available?

The_Lobbster said:

Mercedes Benz tech bulletins specifically states electrical repairs on damaged wires are to be done via crimp terminal only, as solder joints can cause the wire to become work hardened, and therefore a stress break point.

I am a huge fan of the crimp connectors with built on heat shrink, so much easier than using shrink tubing with it separately. I got a cheap kit on Amazon a while back, and the special crimp tool works great.

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This is interesting to me. You will see a voltage drop in a crimp fitting long before a soldered connection. No big deal on a fuel pump or headlight. BIG deal on a throttle position sensor, or similar that .1 volt drop can make a difference in performance.
I try to plan my soldered connections as best I can and have them only is straight sections of the harness. I then try to zip tie around the connections to a secure spot to minimize movement.
The harness on the LJ has well over 200 soldered connections. I have modified several stock LS harness the same way. I’ve had no reported wire failures.
Wire harnesses would cost a fortune to use crimp fitting everywhere and be twice the diameter. I’ll stick to solder and quality 3m heat shrink.

mbryson said:

What would be a "quality soldering iron"? @Greg mentioned the Milwaukee unit. Thoughts on this "name brand"? I didn't catch the brand of my brother-in-law's soldering iron but it didn't suck near as bad as my $8 unit from 20whatever years ago.

https://a.co/d/3RzZUA7

View attachment 178221

I like the temperature readout, the holder dealio, the flux and brass wool gadget and such. I'm sure I'd get what I paid for and this isn't really any better than my $8, 20 year old soldering iron. Although it's probably light years better? Are there good brands to buy? Just buck up and get the Milwaukee unit for $200?


I have yellow tools. For no other reason than Great Basin Supply or whatever was selling them in Moab one year.

https://a.co/d/f7zhiLC

View attachment 178222
....hah!!!! That's not even a DeWalt. I did the same thing on a heat gun. While the heat gun works, it's not that impressive. I don't see an actual DeWalt unit available?

Click to expand...

The most important thing with a soldering gun (YouTube University graduate, here) is the watts output. Some barely put out enough watts to melt solder. Higher watts will melt solder faster and produce better results for you.

Kevin B. said:

Can we talk about Deutsch vs Weatherpak? I'm ready to throw out all my cheap knockoff connectors, but I don't know enough to know what to replace them with.

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A simple Google search will make up you mind quick. Duetsch is better in every way except for cost. Easier to work with, more positive crimps, more configurations, more waterproof.

mbryson said:

"quality soldering iron"

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Weller is the name that come to mind. That's what everything on the shelf at Radio Shack used to be, anyway.

Weller we is what I’ve used for years. Get the hottest one you can. You want to heat the copper fast to minimize too much heat soak and melting insulation. Spread the individual wire strands out like a fan then insert the wires into each other so the strands interlock. Then twist them together as tight as you can. The tighter the twist the better the heat will flow for a faster solder. Be sure to use electrical solder. It takes a very small amount.

I have a Hakko soldering iron and it is a beast. I wouldn't trade it for any other brand.


For joining multiple wires, I use these band style crimp connectors. I didn't know they existed until I took a course on motorsport wiring.


Regarding connectors, I've used a bunch of weatherpack and deutsch. Weatherpack is good but deutsch is great.

If you really want to take your wiring up a notch, check out Raychem heat molded boots and shrink tubing. Racespec carries it but I'm sure tons of other online suppliers do too. Racespec has that really nice tefzel wire too if you want to go crazy.

Proper crimping tools are a must.

lhracing said:

Having been in the Wire Harness industry for over 27 years, I cannot overstress the importance of using the proper crimp tooling. Contact manufactures will identify the proper tooling, this is typically their own tooling. If you cannot get the manufacture's tooling, you should use aftermarket tooling that produces the same crimp.

I put together some information for my son, others may find it interesting, see attached.

Click to expand...

This is some proper wisdom. Thanks for sharing. It's now being sent to my sons.


One "hack" I've learned is that you can slice slivers of glue stick to insert into normal heat shrink tubing and create "weather tight" heat shrink. Works a treat and also supports the solder or crimp better.

spaggyroe said:

I have a Hakko soldering iron and it is a beast. I wouldn't trade it for any other brand.

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I have a similar unit. For soldering electronics, this Hakko is the gold standard. Get a Weller soldering gun for bigger wires and you will be set.

This gun rocks