Eric,

The horn should work alright on 12 volts for short toots. Laying on the horn for 2 minutes might give it a coronary.

Your post indicated that the spring 'melted'.

I am not looking at a diagram, but I think your rig should have a actual horn relay in the engine compartment, and the horn wire up the column should be the GROUND for the coil in the horn relay.

This ground would not be expected to pass much current, only what was required to pull the relay in.

Melting the spring in your contact button makes me think it passed full current to toot the horn.

Could this have been the case? Take another look at the wiring diagram and see if you switched something you shouldn't have. Good luck.

Stuart