Cigarette lighter?

[3dubs]

I found a bunch of threads about where to tap a cigarette lighter. I am wiring to the front battery. But my lighter does not tell me which is positive and which is negative. I can see one goes to the middle to touch the front part of the plug and one wire goes to the outside to touch the sides of the plug. But which is positive and which is negative? It seems so simple but I have been searching the internet and this site but can't seem to find it.

 

[Wartburg]

The one on the outside is the ground. I believe I just grounded to the dash and only ran a hot/positive line.

 

[3dubs]

Thanks, That would have been my guess. It might short the other way around.

 

[K9Vic]

The outside is negative and the inside pin (looks like a bolt) is positive. When you look at a the appliance that you plug into the cigarette lighter, you notice the fuse is inside the plug.