[Fritz]

What type of relay do you have? I had a problem with my horn at first, but figured out that I needed to ground the steering column where the button made contact. That's how my relay works - ground switching contact relay.

For troubleshooting I would suggest making sure you have power to the relay first, then test grounding the relay to listen for the contact switching (assuming it's that type of relay). You should actually hear the contacts switch. Also, I had to search for a wiring diagram for my particular relay to make sure it was wired correctly.

If you can figure out what type of relay it is, it'll be easier to assist you, I think.