Funny, my horn quit today. Found the relay to be the culprit. Look up by the fuse panel. It's the one by its self, just hanging there. Three prong relay, $10 at Advance Auto Parts.
Horn mounts on left fender, single wire hanging out of the wire loom about 8-10" from the radiator support.
Horn button creats a ground for the relay. Power is at the relay only when key is on.