horn, switch, weirdness

[plehman]

It's a 1976 R90/6. Had to replace the switch on the left since the lights didn't operate all the time. Everything went well except the horn. So the lights all work now, but the horn circuit doesn't.

I think it's on the correct pin on the board in the head light bucket. Same as before. The horn was working and I can short it sometimes with a pliers. Yeah, if I go to pull it off the pin the horn honks.

I can also make the horn switch work on other pins. I try the adjacent pin and the horn switch flashes the lights. So the switch itself is working.

You can see the brown/white wire in the attached image.

Not sure what to do next. Any suggestions?
thanks

[plehman]

And the way I consistently short the circuit is to touch the horn wire to two pins. The one it should go to and the next one up.

I can see ohms when I connect the wire (brown white) to the pin (H) and hit the switch on the L bar. So it seems to be the correct circuit.

Argh...

[brentde3]

I am dealing with the exact same problem. Max BMW's fiche says that the new left-hand switches have eight wires, where the originals had nine. Do you have eight or nine?

Anyway, I have eight, and haven't yet figured out how to get the horn to work. Apparently, according to the fiche, the green/black wire needs to plug into the ground terminal. I don't understand it, and it hasn't worked for me yet.

I've been of no help whatsoever. So, I'll just be watching this thread to see what the smarter people have to say:bolt

[Bill Burke]

Remove, clean and replace your two 8 amp fuses in the bucket. The horn is notorious for blowing a fuse. This may resolve your issue.

[plehman]

Funny to hear others having this same issue. The missing wire is Red - just leave that off ( according to Rusty at Max's).

I checked the fuses - looked fine.

[amiles]

you need to attach the green black horn wire on the /7 switch to the brown part of the /6 circuit board.

[plehman]

I tried the green black wire in the H pin and it didn't work.

On the brown white wire I can see resistance between the wire and that same pin when I meter it and hit the switch. So I think this might be the correct circuit.

I'm waiting for a new battery. The old one is strong enough to light the lights. Could it be not enough for the horn? (doesn't really make sense).

Matthew Parkhouse wrote up a horn article in Jan 2009. He suggests a relay. Is that really necessary?

This is very frustrating.

[plehman]

So the horn works if the high beams are on. It doesn't work with the light switch in any other position. I guess that will get me through inspection, but it shouldn't be connected to the light circuit.

Thanks for any advise.

[amiles]

What do you mean by "The H pin?"

Yes the Horn takes lots more power than the light.

re-check where you plugged in the wires, it's a tight spot and mixing them up is easy.

[lostboy]

amiles is correct. The original switch for '75-'76 provided a ground for the horn, via the horn button. This switch is no longer available, and the '77-'78 switch is now provided instead. The '77s, since they provided a positive connection to the horn, require that the green/black lead be connected to ground (brown) on the earlier bikes.

The red lead allowed one to flash the high beam with the ignition switched off, and this has been deleted.

There have been a surprising number of defective switches sold lately, so if yours is connected properly and doesn't work, you may need to return it.

Your supplier may resist accepting a return on an electrical item, but new genuine parts are covered under warranty.

[plehman]

Green/Black to brown? I guess I don't really know what you mean. I tried the Grn/Bk wire in the spot where the brown/white horn switch went and nothing.

I'm calling the pin, the spade connection on the board H because there is a little H under it. I assume that's for horn (same word in German). There is also a brown/tan pattern underneath on the board itself. Sorry this is more confusing than it should be.

thanks

[amiles]

You need to connect to the SOLID BROWN area of the circuit board. There is most likely an unused terminal there.

[plehman]

I'll try that tonight - thanks

[plehman]

I'm beginning to suspect an incompatibility with the switch and the board - if in fact it's a /7 switch on a /6 board. I got it from Capital Cycles and Tommy usually knows what's right.

I tried the green/black wire in all available spaces. There is a brown part to the board at the bottom. Those are empty and appear to never have been used. Didn't work there.

I also tried the brown/white in all available spaces. The best I can do is get the horn to work exclusively with the high beam on. Using the H pin in the brown white stripped portion of the board.

Time to visit my cousin the electrical engineer.

[Bill Burke]

[QUOTE=plehman;452119]The best I can do is get the horn to work exclusively with the high beam on. QUOTE]
I still think you ought to replace the fuses even if they "looked good" - meanwhile, you might see what happens if you replace the headlamp bulb with a known good one (if you have a spare). There might be a short in the headlamp wiring that's creating this problem, or it could be a hidden fuse failure.

[jforgo]

This is interesting.
i am replacing the left swirtch on an 82 RS , and i cannot get the horn to work either. The switch is good, I have tested the fuses in site.
i accidentally hooked it one slot too low and did get horn to work simultaneously with high beam every time. So the horn is also working.
is it possible i have a /6 circuit card in there? Are they the same as /7? How could one tell?

[plehman]

I did it. If you take the Green/Black wire and place it directly over the Brown/white the horn works in all positions (lights off, high and low).
Trial and error, i.e., dumb luck.

You can see the position in the original image (first post). It looks like the red part of the board, one space above the brown/white wire - open in the photo.