1987 Toyota Pickup Horn

My 1987 Toy. P/up has a horn that simply won't work. I've checked the connection at the horn, it's fine. I replaced the center peice on the steering wheel with a new dealer part, still nothing! Just before it went altogether it worked when I would turn the wheel half way around, and then it was only a weak sounding horn. I beleive the problem is somewhere in the steering column itself. My repair book doesn't have any skamatics to help me. Is there a way of "hot wiring" the horn? Or is this a problem for a certified repair shop?

Respectfully
M.F.