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want to hook up horn for my 48 gmc, have horn nothing else, what else do I need

wire would help usually you need a horn relay to activate the circuit while keeping the current away from the horn button, which just supplies the ground to activate the relay and pass the current to the horn .... a factory diagram would be good, one from a Chevy manual should work if you remember to change polarities shown, providing you're running positive ground

Bill

This wire coming out near the bottom of your column is the hot wire, the only other hook-up on the horn is a ground. Under your GMC button is this. It may need to be cleaned up and adjusted.

http://www.flickr.com/photos/advance-design_parts_co/8129344127/in/set-72157631868452754

Brad - I don't believe GM ever put the hot wire into the column, if that wire out the bottom of the column goes to battery + there would be a dead short when you pushed the horn button - the column wire supplies ground to the relay to activate it, the ground on the horn is to complete the circuit when the relay supplies power, and most years the horn ground is supplied by the case mounting

Bill

Two wires I will leave the rest to you electricians.

There was no horn relay supplied with a standard, single-horn Advance-Design truck until 1953. Prior to 1953, a horn relay was supplied with the accessory dual horn kit.

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

I will go by the wiring diagram, thanks for info guys...