All you have is the switch, F12 (15A), the horn relay (under the fuel tank) and the grounds on the horn. I would check the grounds first -look for the brown wire and make sure its connections are tight. It will run all the way back to the battery as BMW does not use the frame as a ground return. Swap the fuse with another one as well often they look OK but are open.
I wanted the use of the great BMW horn on Beryl early on in her life after some cage driver mistook my shape for the invisible man and machine......"huh" how on earth can you not see a bike as large as the LT, complete with headlight on??????? anyway I digress after almost being forced up over the kerb.....tried to give an ample warning but as I have noticed on a couple of occasions merely managed to operate the left blinkers.........bugger.....
tried the horn some ways down the road...spose more of a stress settling exercise than anything else and found the horn didn't work anyway....it's not something that you get to test unless you really need to in an emergency...and then finding out the thing doesn't work is a bit of a mute point.....ok..I'll cut to the chase...the horn button itself was the problem....good mate of mine also had a similar problem and fixed his handlebar horn push button only cos the BMW dealer was on another island to what he was. Beryl was still under warranty so got the handlebar section replaced.
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