A circuit requires a total path from the + batt post to the - batt post. Anything that interrupts the flow of electrons is like an open switch or broken wire. Use a test light in the horn wire terminal and the alligator clamp on the -batt post. Try to blow the horn. The light should illuminate. If it does reconnect the wire and poke the horn housing or braket to get through the paint or powdercoat while someone tries to blow the horn. If it lights now the horn has no ground to the body. You could use star washers under the mount bolt heads to provide a connection. If the horns finctionrd before they should function now, unless they did end up in the oven by some mistake. What is the resistance through the horn? Compare to a known finctioning horn.
