why won't my horn quit blowing

The problem IS within the horn pad / air bag assembly! ... The material inside the horn pad becomes deteriorated and mushy - that allows the horn ground contacts to close - sounding horn without being pressed. An alternative is to have a universal horn button installed in a convenient location to the vehicle operator .. This will save you several $$$. (This repair will not affect air bag operation in any way) The fix will require auto repair skills beyond that of the average DIYer. Good luck!