Ground and/or fuses.
Check all the fuses first. Then your mounting points of the column to the floor and dash. I'm sure something grounds through those. Take a test light and see if the column is grounded, as well as the harness ground point up on the radiator support.
The horn is just a hot wire with a grounded switch. If you can run a 12v to the actual horn, and it works, but the button doesnt, I bet the column is poorly grounded. I had my column loose last weekend and same thing. Horn would only chirp. Bolted it back up, problem solved.