Mine is a 2001 38 FDDS, I just had to replace the horn solenoid on mine, had a meltdown with LOTS of smoke coming from under the dash. The fuse had blown which is a good first indicator, put in a new fuse with instant smoke.
The solenoid was on firewall behind accelerator behind a carpeted panel, you should be able to see the air lines above the carpet. The old solenoid had burnt off completely the 2 wires feeding it, unscrewed the cap and saw that the short extended into the coil area also.
After checking with multiple auto parts houses, Big Rig vendors, and RV repair facilities, I discovered nobody had one locally. Turned to Ebay, found lots of them ranging from cheap Hong Kong/Chinese versions in the $5-10 range up to chromies in the 25-30 range. Had to adapt one of the fitting with an adapter from auto parts house. Good news, horn worked first time after install, but kept on working and working just like the Eveready bunny, pulled fuse and now working on a larger problem with electrical, e.g. headlights/tailights, wipers, and horn not working, even after replacing the master controller.
2001 Alpine 38' FDDS Vin 74378 Cummins 350HP. Baton Rouge, LA