2021. 12. 14. · How to Install 12V Light Switches. Now that you know how power gets sent to a light or multiple lights from the 12V fuse block, it’s time to learn how to wire a switch so you can turn the lights on and off as you wish.This. Answer (1 of 7): We should always wire lights in parallel because the lights have usually same voltage rating and parallel circuits provide same voltage across each end.