......I was just in that circuit yesterday and , as noted by others, there's no fuse in the horn cicrcuit. If the horn still works, then I'd suggest you pop off the horn button cover, remove the 3/4" nut and check the spring loaded contact under the sheet metal plate.
If you down load a shop manual from the Old Car Project you can see a wiring diagram at the beginning of chapter 12. Really helps a lot to see how the horn works.
