'06 ford f350 horn

want to add a set of air horns. need wiring diagram for the horn circuit. 2006 F350 6.0 turbo diesel 4x4 crew cab.

1)Is there an existent horn relay, usually in an under hood fuse or relay box? Upgrade it's fuse (usually also adjacent)to 20 amps and tap the relay output wire. That's one method:- 2) If two wires coming from each horn, either one will be at 12Volts constantly or with ignition on, the other will go to ground when you press the horn. Or more likely, one wire will be constantly grounded and the other will go to 12V+ when you press the horn. In the first case see diagram:- 7F8_relay_1.bmp In the second case tap the wire that goes to 12V+ on pressing the horn.