In 1952 I believe they started using horn relays. For sure in 1953. I don't have access to a 52 truck diagram but the 52 car has a relay. That is when the horn trumpet started having only one hot wire and was grounded by the bracket. The button still grounds a wire at the column, but this time it was grounding the trip coil in the relay to close the main contacts which sends hot to the horn. So the horn you have, if Chevy truck, seems to be 1951 and earlier.
Edit: Dual horns were an option and I believe they had a relay. I've seen a diagram, probably from TCLederman, but can't find now.
Last edited by bartamos; 09/28/2020 4:51 PM.
