I have an 01 Electra Glide that when I disconnect the horn from where it is mounted it works fine but as soon as I put it back in place and tighten everything up the horn sounds like crap. I even replaced the horn not knowing that it still worked as long as it was not mounted in place.
Any suggestions???

 

Horn has a rubber type mount so it can vibrate thus make noise.If horn is mounted firmly against metal,it won't work.

 

Rubber mounted means ya gotta run a ground wire. To test, merely jump a wire from the ground on the horn...to the bike frame. I suspect that's your problem.