@NYBo. The full current drawn by the horn went through the horn contacts on the steering wheel. I guess the engineers knew what they were doing, but I prefer having a relay to limit the current going to the horn button. It only took one wire as depressing the horn button completed the circuit to ground for the relay.
Perhaps a solution for the OP would be to have a non-electric air horn activated by a squeeze bulb. Jack Benny had one on his Maxwell. Unfortunately, the horn would blow at midnight. (I just saw the movie “The Horn Blows At Midnight” starring Jack Benny. I grew up listening to his show on radio).