well, if the 48 GMC didn't use a horn relay, and you don't want to add one, than the horn mount was isolated from ground, the hot wire went direct to the horn, and the horn button wire supplied the ground to a 2nd terminal on the horn .... as I said, a wiring diagram lays it all out

Bill


Moved over to the Passing Lane

"When we tug a single thing in nature, we find it attached to the rest of the world" ~ John Muir
"When we tug a single thing on an old truck, we find it falls off" ~ me
Some TF series details & TF heater pics