Horn issues

[Crashedkiwi]

Hello all;
On my standard unmolested 1975xs650B I'm having horn issues; that is it does not work. It did, and stopped. I've checked the horn itself; its fine when powered directly. I've check the wiring from the horn up to the nightmare of spaghetti inside the headlight and the wires are good. I've taken the switch off the handlebars (wires run through the bars on this model) and the switch gear looked good. - bit then I cam across a post on the forum from Aug 15 2020 called 1978 xs650 se - horn issues. This showed an earthing wire running from the switch which I don't seem to have - did they change switch configurations between 75 & 78?

My assumption is that the horn is grounding the circut when press via handlebar to frame contact - is this correct? I'm going to pull the switch again and check contacts and see if I can firgure out how it's grounding to the bars - but any insight you have will be as always gratefully appreciated.

 

[AUTOMAN]

Think about handlebar grounding also.

cliff

 

[Jan_P]

If i remember correctly the horn has one in Wire and one to Ground
Even though I have been trying to find electrical faults a long time And can find them mostly.
I would consider to pull new wires and having a brand new push button for the horn. ( After fuse or with a fuse )
Skipping the procedure finding it . in the spaghetti wiring which can be heat and water dependent . and then draw new wires.
I would also consider a replacement horn I have used others One From a salvage Mercedes Benz and others or automotive shops and flea markets
Cheap $ 10 .
Cracked old wiring it can take many man hours funding it sometimes. But I would suspect the switch first

Some horns have an adjustment possibility a screw that can need a slight adjustment

 

[5twins]

Does your starter button still work? I ask because it works on the same principal, connecting to the grounded handlebars when pushed. If it does still work then I'd say your handlebar ground is fine and the problem is with the horn button itself.

 

[Crashedkiwi]

Thanks all for the responses; greatly appreciated. Wiring is a dark art on these beasts; nothing is as it seems.
So the grounded handlebars feature here - even though as 5Twins sagely notes, if the ground is out the starter should not work. But it did…
However when you put a multimeter across the ground and the frame, you notice that the last owner has powder coated the top yoke and there is no continuity from the ground wire handlebar/ to the yoke & thus, the frame. Yet the starter works & the horn does not. So you remove the coating to provide a ground & the horn works. and there is now continuity from handlebar to motor & frame. Why? How? Why did the starter work in isolation? Did it find ground via the tacho cable or some other nefarious path? I think I’ll just accept and reflect over a beer. GIft horses and all that.