Peter,

The stock switch would work fine on 12 volts. The only caveat would be if it has on-board circuit protection of any kind. A fuse or thermal would be rated for current flow at 6 volts..this might not offer proper protection for lights etc at 12 volts.

If it does have a fuse or some replaceable type of protection, it would have to be scaled down to cover 12 volts.

Stuart