Where is the wiring? (in the ceiling/walls)

[ZombieCrow]

im wondering how to find out where all the wiring is in the bus, since i might have to drill holes in the walls or ceiling of the bus and im worried i might hit wiring somewhere. is there a stud finder type thing for wiring? the only obvious wiring i can tell that would be in the ceiling area is to the interior lights, but i don't know how to be sure. any help would be great!

edit: i am also curious about this in the event i would want to add a roof rack!

[GoldenGate]

I had to locate the wire routing of all my lights and stuff after I realized that my brake lights didn't work even though the bulbs were good. Turned out to be a very simple fix that I overlooked, but I ended up tracing most of the brake light and other light wiring through the bus.

My dad, a city electrician, brought home a tool from work called a circuit tracer. Basically you hook alligator clips from a sending unit onto a circuit, and it sends a signal through the whole circuit. Then you use a second device to trace where the wiring goes. It beeps loudly when you get close to a wire and fainter when you get far away, sort of like a stud finder. The one my I had the privilege of using was very nice and very expensive, but you could probably find one relatively cheap if you look around a bit.