Have you confirmed the horn itself still works?
If your horn has two terminals one will be battery + Positive (12v hot all the time) and the other is battery - (Negative) that passes through the horn switch. Remove both wires from the horn and figure out which is the 12v + (Positive) with a multi-meter. Reconnect the + (Positive) to the horn. Then use a jumper wire from the battery - (Negative) and touch the other terminal on the horn...did it sound? If not the horn needs attention, if it did then the horn switch wiring need attention.
If you only have one terminal on the horn then you have a relay in the circuit and it switches the battery + (Positive) ...use a jumper wire from the battery + (Positive) and touch the horn terminal and it should sound as long as the ground path is all clean.
Mike B
