On pressing the horn pad can you hear the relay click? If not a Couple of tings check fuse, take the relay out and clean all the contacts. Does the relay click and horn sound?
Second open bonnet and look down the back of the car to the bulkhead, there is a short brown wire that runs from the steering column to the Rack. Check this is ok.
If damaged repair it.
Next you will need your multimeter to trace the earth path from the horn pad through contact ring on back of steering wheel, to the copper tab that sits on the indicator/wiper stalks unit. Sometimes these can break off or be pushed out of alighnment. So It's steering wheel off at that point.
cheers
chalky
On older cars the twin horn set up suffer from current drop through the old wires, so if you disconnect one horn then theres enough to power the other.
