John Clark,
I thought a horn with two contacts indicated the horn coil was insulated and one of the contacts needed to go to ground...or to the horn button, SANS relay.
The truck was originally 6 volt so the horn was also. I assume someone told you to put the ballast resistor (???) inline to reduce the voltage a tad! I haven't heard of this trick before...I wonder if it would work. The horn will sound quite vigorous on 12 volts, and should last forever unless you lay on it for an hour or so. Many folks run their 6 volt horns on 12 volts.
It's a simple matter to use a small jumper and ground the proper contact on the horn relay to test it. This would prove your theory that the button assembly is at fault.
The relay should have three terminals (?), power IN, power OUT to horn, and GROUND through the horn button. This means the horn cannot be insulated from ground itself.
If you were to use a ballast resistor, it would go in the line from relay to horn. This ballast resistor thing is a bit strange...try it and let everyone know how it worked.
Stuart
