How do you fix a horn in a 1989 Mazda B2200 pick-up truck?

Mazda truck horn.

First thing is to locate where the problem is by removing the wire on the horn and attaching a test light to the wire. Ground the test light and have someone push the horn button. If the light comes on, you have either a problem in the horn, or the horn is not grounded. If the light does not come on, the fault is either in the horn button (switch) or in the wiring.