Check to see if there is power going to the horn. Take the wire off the horn and have someone push the horn button and see if you have power at the wire. You may have to turn the ign key on. If you have power then make sure the connector is not corroded on the horn AND wire and you might untighten and wiggle the horn and then retighten the bolt that holds the horn on to make sure you have a good ground, if they checked ok then the horn is bad. They are not that expensive to replace. If there is no power then check the fuse. If the fuse isn't blown check to make sure the fuse holders aren't corroded. If every thing is fine then the problem may be in the horn button area or you have a broken wire. You'll have to get the Bentley manual for your year bug as they all differ slightly on different year bugs.