My air horn is hooked up to use the regular horn button. The compressor is hooked up to only run when the key is on
My compressor only runs when ignition is on also. My old compressor wasn't, and it ran for an entire weekend (powering only my exhaust brake I had no tank and pressure switch). Needless to say, compressor burned up. New compressor installed with tank and pressure switch and relay to only work with key on.
I use a separate horn button as I also wanted to avoid the air horn going off when locking my doors. Especially at 2:00 in the morning!
2004 Dodge Ram 3500 CTD/4X4/DRW/6 Speed
2005 Cedar Creek 36RLTS