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Discussion Starter #1
Hey all! So I recently went down the rabbit hole of trying to fix the electronics on my 1975 Suzuki TS185 and it's a mess!
The first thing I want to get fixed up is the horn, so I went about finding the wires. I'm at a complete loss at this point and was wondering if anyone would be willing to give me any insight. Here's what I know so far, and first off here is the wiring diagram:

So the red arrow is pointing to a wire that has 6 volts running through it (6 volt battery, tested the wire). I found this by just following the wire that came straight from the Rear Break Switch and using one of the splits that was near where the horn should be.

I then found the wire that the blue arrow is pointing to, that comes directly from the switch. I did this by opening up the controls on the handle bar and following the correct colored wire. I assume that the switch is grounding and completing the circuit to the horn. Here are some images of the horn switch and wire:


So at this point I connected up the wires, turned the bike on to make sure there was power coming through... nothing! Now to make sure the horn is getting power I took the wire that was connected to the horn switch and tapped the frame the horn works perfectly.

So at this point I'm thinking something must be wrong with the switch, but looking at the internals everything looks fine... except for one thing. The diagram above shows that one end of the switch should go to ground, but theres only one wire coming out of the switch. Is something wrong here? I have no idea where ground should come into play with this switch. Does anyone have any ideas?
 

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The wiring on many old bikes left a LOT to be desired.

It is possible that the horn switch was depending on the mounting bolt/screw at the switch to be getting a ground from the handle bars.
Or there is supposed to be a ground wire going into the switch "cluster" that connects to the switch internally.

You have done a very good job of chasing this so far.....and you are really close to the solution. Don't give up now.

Do you have the switch cluster OFF of the bars by any chance ?
Or the bars loose from their mount point ??
 

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Thanks for the kind words and advice! I feel so close too it's been bothering me for weeks.

The handle bars aren't grounded, as I can touch the ground wire for the horn to the bars and nothing happens. The handle bars aren't loose in any way but maybe there's some wire that is supposed to connect to the bars and ground them? That seems a bit weird to me though.

Also when the switch cluster is mounted on the bars and I touch the ground for the horn to the metal casing of the switch cluster it makes a VERY feint noise. I could only imagine a wire is loose or something but I don't see any wires going from the cluster to ground. They only lead to the head lamp and turn signals.

The other I don't think there should be a ground wire going into the switch is that there isn't one on the diagram... but I could be totally wrong about that.
 

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The other I don't think there should be a ground wire going into the switch is that there isn't one on the diagram... but I could be totally wrong about that.
You can see the diagram better than we can but it looks to me like there is a ground symbol on the diagram right below where it says "Horn Switch".
If so, that probably means the bars SHOULD be grounded.......and that is the root of the problem.
 

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So I ended up running a ground wire that connects to the bolt on the switch and it works! I just didn't want to carve out any paint on the bars and then have to go through making sure the bars were grounded.
 

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As you progress through your fixes, you may find that you need a good ground on the bars for some other things too.

On the old Hondas, the front lights would stop working......and the fix was to run a ground strap around the steering head bearings.
Yes the ground went THROUGH the bearings.
 
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