Replaced the fuse several times? Should we assume it is blowing these fuses each time? What else does the fuse serve? Do you have a 12V relay or a "good" relay. Did you just try grounding the horn case real good, disconnecting the hot wire, rig a jumper from the battery, and tap it on the hot terminal of horn a few dozen times?
History here says a resistor is not needed. The horn should work. If it blows a fuse, obviously it won't honk after that. So something is blowing the fuse. A resistor is not the answer.
Test it as above, no relay, no fuse, no horn button, just tap and honk. Increase length of honk a little to two seconds-three seconds. Report results. BUT let us know about the fuse ASAP.
1. Corroded horn contacts. Burnt contacts. Broken contacts.
2. Bad relay.
3. A short.
4. What era is the horn from? 1942 or ?
5. Fuse too small.
"too much" voltage to horn is not the problem.
