Rick,

With the battery disconnected, you won't have power anywhere...period. A 6 volt relay would probably fail quite quickly when powered with 12 volts.

Your relay sounds like it was wired incorrectly though. A typical relay should have three terminals, and hopefully they are marked somehow.

One terminal would have a larger gauge power wire attached to it. Another wire of maybe the same gauge would go to the horn. The third terminal might have a small gauge wire that travels up the column to the horn button.

When you push the horn button, you supply a ground to a little coil inside the relay that closes some contacts and allows current to travel to the horn to toot it.

You might already understand how this device works, and it is pretty simple to wire up. Good luck with the new 12 volt relay.

Stuart