Quite frankly guys..I don't know much about the guts of these bikes...and I don't know the brand of the horn either. The guy we bought it from said that when he installed it he used a relay? I have no idea what that is. My dad bought the bike a while back and then just gave it too me so I don't know a whole lot about them besides regular maintenance. My dad suggested it might be a blown fuse but I wasn't sure what you might think? Possibly just a loose connection because it was working one second and then just stopped.
The main reason people go to an aftermarket horn is to get something much louder than stock. The typical thing to do is to wire it using the stock horn wire to provide switched power to initiate the relay. Most installs will be directly off the (+) battery terminal which you can see when you pull the seat off. The relay and direct wiring (hopefully with a fuse) is to provide more amperage to the device than the stock wire / fuse setup might provide. The "relay" can be anything from a higher end protected unit to a 5 buck radioshack special. rw