If I am using a switch that is rated for 16A @125vac in a 12vdc application does the amp rating of the switch also change?

The amp rating is based on the gauge of the conductor. If you need 16A of 12V, you should use the switch to throw a relay.

Ohms law. Amp x volts=watts watts/volts=amp

Actually, that's Joule's Law. Ohm's law is V=IR.

Use the DC rule of thumb: the highest AC amperage rating on the switch should work up to 30 VDC. In this case, the switch can probably handle 16A up to 30 VDC. But this depends on the switch...check the specifications if in doubt.

Thx, it's just a small winch motor that makes a 30 sec run once a week. I wanted to be sure the switch was large enough.

EDIT: I'm guessing it's less than 4 amp