Quote Originally Posted by jerry clayton View Post
the grounds are never interrupted in lighting systems---only for some computer controlled things where they need to reduce the amperage to reduce heat in the computer
Most dome lights have the ground wire running to the door switches, and in parallel to the headlight switch on the old pull on, rotary dimmer for dash lights, and all the way left or right for dome on style switch. Other circuit applications put the switch in the ground lead so that the switch can have less current capacity and be less bulky.