Thanks Hazard ... that's why I said "I also have a relay that came with the horn. Can I just use a relay without and voltage coming back into the Arduino and frying it" in my first post... it's been ages since I've messed with electrical components but I do remember the purpose of a relay is to use a smaller current (and wiring) to send a signal to switch on a higher current. Just couldn't remember if the relay might have any kind of back flow to the board. So it's as simple as a pinout signal to the relay?