That sounds like a solid idea (purchasing older wiring harness). I assume you mean something like this
https://ebay.us/m/bjRUMg
Part of me wonders how much I want to try to untangle this. Overall everything works, except the horn. The wipers go, the wiper motors work (well, after I replaced one), the lights turn on, etc. It looks chaotic as hell there but maybe it’s a controlled chaos and I shouldn’t mess with it, especially because it’s something uncomfortable and tight quarters there. Just seems so wrong to leave it though…
And how did you know it was the contact and not any other part?
My horn contact diagnosis was easy, the contact tip was broken. You can test the circuit and the slip ring by testing the wires that go to the horn. One should be hot, and one should should short to ground when the horn button is pressed. You'll need a willing assistant since you can't be in two places at once.
The horns, being exposed to the environment at the front of the car, get rusty and seize up as seen in the photos posted earlier in this thread. Derusting with Evap O Rust or a generic version can go a long way to getting things going. Followed by cleaning contacts of course.
Everything used to be rebuildable, but that slowly went away as parts producers figured out how to make parts cheaper and faster. Original parts are part of the charm of our cars, but I won't think twice of replacing my original starter with the newer version which is smaller and more powerful.
No, the harness you posted is too new, in my opinion. Cars that new have radically different electrical systems with different load, connectors and probably some color codes. I'd suggest something from a car about a decade newer than yours, like this one.
https://www.ebay.com/itm/157314170182
Goodness, prices have risen since I started working on cars.
Yes, it's tempting to leave well enough alone. Tracing electrical circuits can be time consuming, but I'd be concerned about the condition of your wires since you can't be sure how well those connections were done. At the least I'd give them all a tug to make sure they are solid and possibly give the a wrap of electrical tape if there was any hint of copper showing. There are products that will put a signal on a wire that you can follow with a probe to trace where the wire goes that's useful when you don't have a proper color code to confirm you are working with the right wire.
I've also seen a little 3D printed jig that allows you to use a paint pen to put your own wire trace on a wire you are wanting to match to a standard color code, assuming you are starting with the correct base color wire that is. You could do that piecemeal if you just need to replace a few wires rather then spending a bundle on an entire old harness.
Oh, and check your fuses, the fusible link on ceramic bullet fuses tends to oxidize over time and can cause issues with trouble shooting. I had a tail light that showed 12v but wouldn't light up. It turned out that the fuse was oxidized and would let a trickle of voltage through but not enough current to light the bulb. It would be the same for a horn as well, but since you applied 12v straight to the horn and got no joy, you know the horn is in need of help.
