Help with wiring please

[panheadpete]

Hi Paul; Idon't know 45 wiring but on general principles, if a horn button has 1 wire to it, it's to earth the horn, which should have a live feed to it and the other connected to the horn button. That's the way most older systems worked. A horn button that has two wires would be feeding live to the horn UNLESS one of those wires should go to earth - the wiring diagram will show that.
One way to test which system your horn should work on ; does it have one terminal or two? If one, then that should have the live from a two-terminal button connected and the horn body makes the earth.
If two terminals on the horn then almost certainly one is for a permanent live and the other goes to a single terminal button - unless, as above, the diagram shows a separate earth from the button (same effect as a sigle terminal button), or the horn needs a separate earth - again, the diagram should make it obvious where the earth for the horn circuit is, at the horn or at the button.
Cheers,
Pete

[panheadpete]

Just had rummage through what I laughingly call my 'library' (a large quantity of cardboard boxes, randomly scattered) and found the 1942 Motorcycle Mechanics Handbook from The Armored Force School, Fort Knox, Kentucky.
The wiring digram, June 11, 1941, shows what you have already seen, that there is one wire to the horn button with the live to the horn coming from terminal 4 on the ignition switch.
So, the button earths the horn - test that by connecting the live feed to one side of the horn and earthing the other; then the only purpose for two terminals on the button is for one to go to the horn and the other to earth, although a two-terminal button is usually used in a live circuit, it will work the same. (The diagram only shows one terminal for the button).
Cheers,
Pete

[dodgyloner]

Hi Paul

Pete's right - from memory the horn button earths the circuit when pressed. Suspect you got another bad earth and need to clean up the area or run a separate earth wire. My own preference is to separately earth everything forward of the headstock with separate wire(s) back to the main frame, otherwise you're relying on everything earthing via the neck bearings which isn't perfect.

Re the wiring - if its filthy a little white spirit or similar might lift off sufficient of the grime and ageing so you can see the tracer threads in the cloth covering. Don't overdo this as it may have an adverse effect on the old wires.

I'm up in Yorkshire (and it is the bl00dy Grim North at the moment!!). Let me know if you want to discuss selling Military parts etc.

Karl

[English Steve]

I have just fitted a new horn switch on mine - according to the wiring diagram from the Tech Manual (1943), there should be a single black wire to the switch from the horn, and a green wire from the horn to the signal light terminal by the oil pressure light. This then links to terminal 4 on the ignition switch via a black wire. As previously said by Pete and Dodgy, the switch earths to the handlebar when pressed. I got a NOS switch from Fred Warr and a complete military wiring loom from 45 Parts in the Netherlands.

Hope this helps.

[Paul1]

Cheers for the info guys, so as i have a switch live from terminal 4 on the switch to a terminal on the horn and a second terminal on the horn, i reckon if i have got 2 black wires from the horn button, if i connect 1 to the 2nd terminal on the horn & take the other back to the main earthing terminal under saddle, when i press the horn button it closes the circuit and should make a noise.

Will give it a go and see what happens.

Thanks again & fingers crossed.

[Paul1]

Success it works don't know if my neighbours will appreciate it at this time of night !!!

Thanks again for all your input.

[panheadpete]

If we're wrong, PM BaZa - he knows how to put out fires, allegedly
Cheers,
Pete