65 Dart Horn Problems

No wiring does not work that way. Only "hot" is at the relay. Wiring to column, copper wheel thingy, horn switch attached to steering wheel face are all an open ground. Taking the system to ground honks horn. Yes to helping isolate the problem area based on which component triggers it. Mine is a simple method, nothing wrong with the volt meter/continuity test method either as described by 67GT273? but you need the tools and familiarity with using them. I'd remove the steering wheel and set it aside. Plug in the relay and see if it honks or is quiet. With steering wheel still off, do the column connector test I described.