I have an 18 T with a 6 volt horn that does not want to work. I rebuilt the horn, put on a new horn button and new wires and all it just clickes and thats all. After I rebuilt it I bench tested the horn and it worked perfectly. One wire is from the horn button and the other wire goes to the ground and the horn body is also grounded but no cigar. Any and all suggestions welcome. Frank
Check voltage at wire from horn. It maybe wired to ground horn when you push horn button. If that is the case run hot wire to button or unground the horn inside.
"One wire is from the horn button and the other wire goes to the ground and the horn body is also grounded but no cigar."
Do any of these wires actually go to the battery? Looks like the horn is grounded and so is the power wire.
1918 unless converted, would be a mag horn. a wire from the mag to the horn, a wire from horn to ground (horn button) Don
Did you bench test the horn using an AC transformer and now you are hooking DC to it from the T battery? DC battery power would cause only a click to a magneto horn. Post a picture of the horn or look down into the snout (actually called the "bel") and see if you see a screwdriver slot and a locking nut in the center of the horn diaphragm. If you do see that then you have a magneto horn and it must be supplied with magneto power and the motor has to be running for it to work. If nothing in the center of the diaphragm then your horn would be a battery horn with points inside and it might just click if you don't supply it with full 6V power. Battery horns draw 5 amps so you need at least a 16 gauge wire with good connections at both ends. I would use 14 gauge wire since your 18 T would have 16 gauge wire for the magneto horn and the mag horns only draw 2 amps from the magneto hence you can use the lighter 16 gauge as original. Ford did use 16 gauge wire with the battery horn starting in '22 but it is kinda light for the application.
The 1918 started using the combo switch/horn button. While I agree your wiring connections will work, it might be confusing because on an 18 the magneto "hot" wire went up the column to the combo button/switch and then the button completed the connection to a wire that ran down the column to the horn which had only a single power connection with the other connection being grounded either externally or internally to the horn housing itself. If those parts are missing then your method might be simpler to rig up and it WILL work if the horn has 2 connections on it with neither of them grounded.
John: You are right, I was thinking my 16. When he said it just clicks I thought mag on 6V just clicks. Don