in the left hand wing behind the bumper there is 2 horns, check the connections out unplug then and if you can clean up the pins, spray some electrical cleaner in bot sides and when fitting bk together a smear of vaseline round the plastic, and in the connetor should stop any water getting in for future, you could also take the horn of and turn it upside down and put it on the radiator to dry it out, if your still stuck see if you have power going to the horn its self and see if when the horn is pressed its switching the earth( cant remember which way round it is but i think the earth is switched) hth