Your '76 should have the little relay on the passenger side panel. Is it fully hooked up and functioning? The wire to the wheel button only completes the ground circuit, so you can test that stuff fairly easily.
There should be a large Yellow wire with a fusible link running from the relay to the starter relay/solenoid where it gets it's power.
Next there is a Yellow w/green wire that goes to the horn itself.
Then a Black w/yellow wire goes up to the horn button.
The relay itself must be bolted to the fender (for a ground) for anything to work.
Some tests might include:
Run a wire from the battery to the horn directly, just to make sure that it's still capable of working.
At the connector to the steering column, tap a wire into the Black w/yellow wire and run to ground. Each time you ground it, you should hear a click from the relay. You should be able to hear it from the passenger compartment, but if not, have a helper listen and/or feel the relay for the clicking.
With an electrical tester, make sure there is power all the time from the Yellow wire. You can pull the triangular shaped rubber connector off of the relay and push the probe right into the socket there.
Good luck.
Paul
