brendan,
I have electrically confused half the forum this evening....it's your turn in the barrel.
If it is a old truck with a conventional horn..no relay, then mashing the middle of the steering wheel grounds the horn. It is wired with a hot already. When you ground the horn, the little vibrator is suppose to do it's thing.
You can run a wire from a good clean ground point, and touch it to a good clean point on the horn. Don't touch it to the other wire.
The ground wire you touch should spark a little and if all is well, the horn will sound. At the very least, if is quiet, you should hear a funny sounding attempt to toot..sort of like a growl.
You can coax it to toot, as you hold the ground wire on it, by tapping it with a screwdriver.
It might have an adjuster/locknut assemble on the underneath which is used to fine tune the tone. Fussing with this usually silences it for good. Have fun!
Stuart
