Adding Exterior 12v Light

[Adony]

I am thinking about installing another exterior (porch) light near a constantly used external storage compartment access but I have one problem. I can connect the new lights 12v positive lead to a source from a nearby 12v light switch but can't find a place to pick up the 12v ground (negative). The trailer is metal sided and has continuity between it (siding) and the trailer frame (checked with VOM)... can I safely use the metal trailer skin as the new lights 12v (-) connection point?

[sherdep]

if you hook your meter up to the +12 and the skin and get +12 on your meter it is considered a common ground - I dont see why you couldn't use it as the ground for your light
it would be no diffrent then using the trailer frame as your common ground as well.

[Goomph]

What sherdep said, you can always use the trailer frame/sides as the ground. My old tent trailer had no ground wires to the lights at all. They just used a screw to provide ground by directly connecting it to the frame/siding.