[Stocker]

Welcome to the board! I'll try to help you, but if not, there are a lot of experts here, and they are eager to offer advice. As designed, the horn circuit is pretty simple. However, a prior owner may have altered yours.

Pressing the horn button sends ground (on a black wire, iirc) to the horn relay on the inside of the firewall, under the dash. The relay then operates and sends 12vdc on a green wire to the horn(s). That's it in a nutshell. If you lift the green wire from the horn, you can troubleshoot the circuit without the horn blowing.

It sounds (no pun intended) like your black wire between the horn button and the relay is getting grounded by the clutch, or something near the clutch. Good luck, hope this helps, and keep us posted!