I have a 2002 Windsor so it may be different but in my front drivers side electrical bay under the drivers window I have 2 small fuse/relay boxes. In my Monaco 1 box there is a 20 amp fuse PLUS a relay that controls the air horn. I would check for a fuse first and the the relay.
On my coach the horn air, the solenoid is located in the upper cabinet above the drivers seat behind the cabinets. Not an easy way to access, I found mine when I replaced the old analog TV.
You symptoms suggests possibly a failure of the relay, causing the horn to come on and then possibly fuse blowing. Just a guess.
2002 Monaco Windsor 38 PKD Cummins ISC 350 8.3L
2005 Jeep Grand Cherokee w/5.7 Hemi