Making a Wiring Harness

[andrew90]

I have a wiring harness that's in bad shape. Lots of the wires disconnected from each other and some are just destroyed. I thought it would be best to do a whole new wiring harness but not sure I'm capable. I've read several of the electrical posts in the forum and feel like I have a pretty good grasp on the basics. Any suggestions?

I do have the wiring diagram to the bike.

 

[Barnburner]

Have you modified any of the electrical systems on the bike? If not, then it may be best for you to just eBay a new, or at least good condition, stock wiring harness. If you have modified things then a new harness may be worth it. It's not that hard to do but will take some time to do a good job. There are several good examples on here where members went through their stock harness and simplified circuits and added modern components. If you want to go that route, order new wires from the gentleman here on DTT that sells a bunch of colors in 25 ft lengths (Mark13018 is his username), a connection kit with crimper from Les at Vintage Connections, and your choice of wire covering (I chose abrasion-resistant braided wrap). Or, you could just order a badass one from SparckMoto (Sonreir here on DTT) and have him do it all for you.

 

[Sonreir]

Plan the functions you want for your harness and understand what each wire is doing. Until you understand the purpose each wire serves and how it accomplishes that goal, it's unlikely you'll come out with a working harness at the end of things. After that, do your layout so you ensure that your measurements will all work out (measure twice, cut once). From that point, you should be able to wrap most of the wires in heat shrink or harness tape. Connectors go on last. Test each connection with a multimeter to ensure current will be flowing without too much resistance. Under an ohm is usually OK, but you should be able to get around half an ohm with properly stripped and crimped connections. Also test to ensure that NONE of your power wires have continuity to ground or you will blow fuses or cook wiring as soon as you plug it in.

Expect to spend about $30 on the wire you'll need (unless you're going with a very simple harness), $90 for the connection kit from Vintage Connections (one of my very best investments), and another $30 on misc parts like heat shrink, solder, harness wrap, etc. Double these prices if you're buying from an auto store instead of online.

 

[andrew90]

Thanks for the input. That info definitely gives me a start. Just not sure I'm capable of doing a whole wiring harness myself. I can make sense of it all but not sure I have the hands on knowledge. And unfortunately don't have a mentor that's experienced in electrical on bikes.

 

[Sonreir]

The other option (which might be easier for a newbie) is to run one circuit at a time. Test it to make sure you're getting the results you want, then do the next circuit. Repeat for each circuit until you have a working harness. Then you wrap the whole thing and call it good. Make sure to have a box of fuses on hand as it's pretty likely you'll cook some. Never run any wires directly to the positive terminal of the battery without first going though a fused connection. This help keeps your bike from catching on fire.

 

[irk miller]

The other option (which might be easier for a newbie) is to run one circuit at a time. Test it to make sure you're getting the results you want, then do the next circuit. Repeat for each circuit until you have a working harness. Then you wrap the whole thing and call it good. Make sure to have a box of fuses on hand as it's pretty likely you'll cook some. Never run any wires directly to the positive terminal of the battery without first going though a fused connection. This help keeps your bike from catching on fire.

While working on a 78 Coupe de Ville I customized, I did not heed the whole fuse connection warning and caught my a/c unit on fire. My wife called the fire department, who luckily were the next block over. After they put out the fire, I had to endure another thirty minutes of rousing by the brigade. It needed new paint on the hood and all new wiring on the passenger side. The moral of the story- fuses are our friends. ;D

 

[andrew90]

Got it. Fuses are friends. Going to study a little more and see if I want to dive into this project. If not, I may call on Sonreir to do me a custom harness.

 

[Flugtechnik]

When I did mine, I basically did it just like Sonreir said, one circuit at a time. However, instead of measuring, I put the wires on the bike and held them together and in place with zip ties every couple of inches. As I added the circuits, I just added more wires and routed them as needed, removing zip ties and adding the new wires. Once I was done, I removed the zip ties one by one as I wrapped the harness. I went through a lot of zip ties but they are cheap and I knew the harness would be exactly where I wanted it.