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???

 

As you know, a horn is a pretty simple device.
If it works anywhere is should work most everywhere.

If the horn/wire tabs are clean and free of corrosion, and the wire clips are tight when you push them onto the tabs, I'm thinking that you may have a wire that's broken "internally" and you'll need a test light or a meter to trace your problem.

 

When you test the horn off the bike and it sounds fine, what are you using to power it? Is it the same connector as you use when it's mounted on the bike, or are you using something else like a battery charger or jumpers from the bikes battery?

If you are not using the bikes horn connectors, when it sounds good, but are when it's mounted and sounds bad, you've likely a voltage and or current problem on the bike. Low being the most likely.

 

If your horn is mounted in rubber (like mine is), try tightening or loosening the screws in the rubber mounts a bit. If they're not just right, it can dampen the vibrations of the horn just enough to muffle it. It's happened to me.

 

^^^^This^^^^
If your overtightening everything it puts stress on the diaphragm and will make the horn sound like crap.

 

^^^That.

Had the same problem on my 2014. I mounted a cooling fan and no matter what I did, the horn was muffled. Finally had to ditch the fan. Even at that I had to fiddle with the horn to make it sound right. If I tightened it up "too much", it totally dampened the sound. Loosen the nut some and back to being loud. Weirdest thing. My guess is not all horns are affected.