If you have a voltmeter, I would next test the horn switch itself - I believe that the BMWs up through 84
had the power wire going through the switch to the horn, rather than on other bikes which used the switch
to complete the ground circuit to the horn. you should see +12V on one of the leads that plugs into the horn
only when the switch /button is pressed. If you not, then I'd look for corroded contacts, broken wiring, or
(hopefully not) a broken switch as the cause of the problem.
If you have dual or non-stock horns, such as the Fiamm, it is very possible that you do have a relay to engage
the horns, as they draw alot of current and more than what should be allowed to go through the horn switch
itself. In this case, the horn button sends power to the relay coil, which closes and sends the main power
from the battery (there may often be an inline fuse in the wire harness here) to the horns. The relay, if youhave one,
is usually under the gas tank toward the rear. Do you have a digital camera that you might snap a pic ?
