There are many ways to learn, but few to none of them compare to that of spending time standing over the shoulder of a master of the craft. This awesome page sent in by [JohnU] is a fantastic corner of the internet that lets us all peek over that shoulder to see someone who’s not only spent decades learning the art of of creating cable harnesses, but has taken the time to distill some of that vast experience for the rest of us to benefit from.
This page is focused on custom automotive and motorcycle modifications, but it’s absolutely jam-packed with things applicable in so many areas. It points out how often automotive wiring is somewhat taken for granted, but it shouldn’t be; there are hundreds of lines, all of which need to work for your car to run in hot and cold, wet and dry. The reliability of wiring is crucial not just for your car, but much larger things such as the 530 km (330 mi) of wiring inside an Airbus A380 which, while a large plane, is still well under 100 m in length.
This page doesn’t just talk about cable harnessing in the abstract; in fact, the overwhelming majority of it revolves around the practical and applicable. There is a deep dive into wiring selection, tubing and sealing selection, epoxy to stop corrosion, and more. It touches on many of the most common connectors used in vehicles, as well as connectors not commonly used in the automotive industry but that possess many of the same qualities. There are some real hidden gems in the midst of the 20,000+ word compendium, such as thermocouple wiring and some budget environmental sealing options.
There is far more to making a thing beyond selecting the right parts; how it’s assembled and the tools used are just as important. This page touches on tooling, technique, and planning for a wire harness build-up. While there are some highly specialized tools identified, there are also things such as re-purposed knitting needles. Once a harness is fully assembled it’s not complete, as there is also a need for testing that must take place which is also touched on here.
Thanks to [JohnU] for sending in this incredible learning resource. If this has captured your attention like it has ours, be sure to check out some of the other wire harness tips we’ve featured!
How does it apply to CAN signals? They degrade quite badly when used in non-compliant connectors.
No offense but I’d rather my car not loose brakes just because of shoddy Temu connector.
I’d be more concerned about the hydraulic connectors…
I made the sata dvd rom drive in my Xbox 360 external. Used a cool looking molex plug, crimped the pins, and it didn’t work. All the pins were connected properly, I assume it’s due to lack of insulation or something like that on the plug. Next time I’ll use a proper sata plug.
I’d say that’s just bad connectors in general that’s the problem, rather than CANbus being fuzzy.
And CANbus is surprisingly tolerant, so again, shitty connectors with lousy or nonexistent coating to prevent corrosion, ass garbage pin-to-pin connection tolerance, practically worthless grommets/gaskets to prevent moisture ingress and just awful crimp ends (and often also crimp tools bundled)
Best connectors to get off-brand are the Deutsch style ones, but that’s because they’re overdesigned, and thus fairly large and clunky.
send them over stp ethernet
Only if those come with a neat oval sticker…
https://upload.wikimedia.org/wikipedia/en/thumb/9/9a/STP_%28motor_oil_company%29_%28logo%29.png/250px-STP_%28motor_oil_company%29_%28logo%29.png
What bothers me the most is that car manufacturers do not design to ease of repair, at all. The result is crazy wiring harnesses that are total non-sense and no way to tell if a CAN bus device is connected, not connected, or merely malfunctioning. Proper cable management could be built into the car design but wiring harnesses are optimized for cost. Naturally, when it comes to repair/diagnostics it’s a labor intensive process based on arcane knowledge unless you buy very expensive custom tools for that exact car’s make, year, and model.
Wiring harnesses may seem nice at first glance but they are mostly bullshit that’s used to cut costs at the expense of repairability.
s/Wiring harnesses/Cars/g
there. fixed it for you. there is a reason i drive a 30+ year old car. i can dix it myself very cheaply…
Just don’t dix it while the exhaust is still hot :)
My car is pretty new. It’s only 17 years old. I investigated a lot of things on this model before buying it as I didn’t want any CAN nonsense to get in the way.
Colleague had a car from that era and his car often would just turn off while driving, turned out the radio had issues. Everything died, engine off, because of a radio. Was helping a friend, his car had major issues after we removed his from bumper for repairs. We tried starting the car without his front bumper connected. That was a huge mistake.
Dodge is awful for that, they buried the fuel pump inside a main, unsealed, electrical panel, in the fenderwell. Do not understand.
Fuel pump relay^^
Don’t know of any fires due to the location of the fuel pump….
These things get thought about well before manufacture Some here may remember the old VW bug (split windshield) had a gasoline heater, it worked very well. Thank GOD for German engineering.
This is a dying Art; making wiring harnesses. I am less than good at the old school way of wax coated lacing tape and peg board. That was a nice thing about Heathkits. They did the hard stuff for you like make those wonderful wiring harnesses.
That is annoying. And the more I learn about industrial design, the more I learn why that is.
The engineers are trying to squeeze every last centimeter to make things tighter, and lighter, for emissions. Designing for manufacturing – they have to be able to put it together. Heat. Vibration. So many things. Repair is pretty far down the list, a long list.
The parameters are very different than they were before the mid 1970s, and getting more different every year. In the 1960s up until the oil crisis, they could make cars BIG, with lots of room for everything. Then they had to shrink everything, while fitting in a lot more equipment. Since then they’ve had to add miles more wires. I’m starting to understand why ease of repair is sacrificed.
Wow! I never knew that “wiring porn” was a thing!
My first job out of tech school was with a defence repair contractor for the Canadian military. I gained an appreciation for neat and logical wire harnesses there; but the materials, tools, and techniques described in the Motorsport article are light-years beyond those used on that old radar and nav gear.
My first job was with a contractor for Ford (flashbacks) making those on slowly moving jigs on a line till I moved up to machine maintenance. We made what they claimed was the most complicated harness in the world for the high end Lincoln Mark IV. The densest part was as thick as your wrist. We also made the long skinny one that ran back to the tail lights past the back seat bar-b-que on the Ford Pinto. In those days Ford would run 12v to the dome light switch in each door post and a second wire back to the light, rather than grounding the light with one wire only to each door, extra wiring. They were having quality issues and then it all went to Mexico.
Extra points for the subtle “back seat barbecue”. 😂
I was trained to make and repair wiring harnesses for the avionics on fighter aircraft – looking at modern cars is just an exercise in shaking my head.
Anyone familiar with electrical engineering concepts will know that the brand or the amount of money you pay for a connector has absolutely nothing to do with its ability to conduct electricity. I.e. Gold plated connectors are worshiped but are one of the least conductive materials you could use. A “copper connector” from any supplier will conduct electricity equally well. Making solid connections is the important thing. For those of us who prefer to do things ourselves, this is another fine example why we can, and should.
Gold does better against corrosion than copper, but for the price difference, copper is preferred. To say gold is one of the least conductive materials is just scientifically false as silver, copper, and gold are the top 3 conductive metals that exist. Now that isn’t to say different companies use a different % of gold in their gold plated cables, which is likely the real issue.
Unintended consequences are beginning to pop up with more complex and environmentally durable harnesses . Fluids (usually something under high pressure – oil or antifreeze) may migrate from a sensor with a failed seal through the insulation on wires in the wiring harness to exit somewhere else in the system, since there is no drain on the individual wires and the connectors themselves are robustly gasketed.
You know those jokes about “blinker fluid”?…
Land Rover’s TD5 engine harness is renowned for oil migrating up the loom into the ECU, that’s old hat now.
Just wait until we have ai designing our harnesses… could prove useful, or probably disastrous haha
I’ve read parts of it so far. This is the best thing I’ve read in a long long long time.
The printer is rolling. 102 pages, so 51 sheets of paper. Worth it. I need a hardcopy of this. I just ordered a bunch of stuff for making wiring looms. This will be a very very interesting read.
I’ll never make it this nice because those connectors and equipment are just out of my price range, but I’m trying to make the best wiring looms I can.
as an aspiring race car builder, I recall the first time finding this page and reading the entire thing.
It’s comforting to know what the “best” is, and to happen across a comprehensive description. As someone who rarely skimps on parts and tools, it’s also sobering to know for certain I won’t be able to wire to this standard.
Service loops, milspec connectors and boots, resin potting, concentric twisting, and $500 crimpers are out of reach for me as a DIYer. However pretty much any wiring application can benefit from high-quality mechanical crimps as compared to soldering, 3:1 adhesive-lined flame-retardant heat shrink, fully-sealed connectors like weatherPak and knock-off DTMs, RayChem harness heatshrink as compared to electrical tape, and proper abrasion-resistant loom as compared to the split corrugated plastic crap.
Bit late.
I fully agree with your statement. It’s way out of my price range. I crimp everything and for testing only I use wago 221’s. I got many rolls in different sizes of heat shrinks. going to look into weatherpak and knock offdtm’s etc. thanks for those tips!