65 Dart Horn Problems

Don't overcomplicate it. The horn wire comes from the relay, through the column connector, up the column, and to the horn switch/ button section.

So first unconnect the column connector and satisfy yourself that it is not in the horn relay or wiring to that point. Now, with the column isolated, and the wheel off and the button components separated, you can put a meter/ test light on the horn switch wire to ground. Wiggle that wire and the top area where it interfaces with the horn switch. You can easily figure if that wire has an intermittent short

MOST horn problems of this nature are "right there" in the switch area---either the switch itself, or the interface between the column wire and the brush/ roller contact setup