I'd pull the wire connections off the horn, clip a volt meter to the two wires (one side of the horn may be grounded in which case you clip the + probe to the horn wire the other to ground) press the horn and see if it's getting 12 volts. If it is, the horn is bad, if no voltage the problem is either the horn switch, the horn relay if there is one (see the wiring diagram), a loose wire or bad ground...or less likely, a fuse. My vote is a bad horn. Please report the solution.
