Greetings from LeonSprings, Texas USofA, Have done a search on this problem without a thing being found. The only time the auto horn is used is when inspected. It is due this inspection and now the horn will not work. Found the Horn Relay under the dash/right side of Glove Compartment also checked the voltage and it is there when pressing the horn on steering wheel. NO voltage on the horn most all locations tell you there should be 12 volts on the horn at all times, WRONG, on this car it seems this is supplied through the relay when pressing the horn. Have not found any manuals that have any information on the horn system for my car. My area of expertise is Journeyman Electronics Technician and own general mechanic on my own vehicles. This one has me stumped . . .

The horn pad/contacts merely ground the relay, so there is 12v at the relay, then the relay is grounded by the horn pad, and the relay sends 12v to the horns, thats how it works so get out the dvom and see whats what.

The horn button is a ground for the coil side of the relay. As long as the ground leg of the coil isn't grounded, there should be voltage on both legs of the coil. My info shows a 20 amp ctsy fuse, hot all the time, for the horn circuit, supplies voltage to both the coil and switch side of the relay. With the relay unplugged, there should be two terminals that are hot all the time. If you know which relay terminal supplies voltage to the horn, you could use a jumper and run B+ to the terminal, the horn should honk like crazy, regardless of the horn button. I'm not an electrical expert,but, that's how I see it.

Hey Max, you beat me to it, good info.