Duster Headlights not working even with power?

Yes pluged a wire in the negative side of the socket plug then clamped the other end of the wire to the negative prong on the back of the headlight then I took another wire and ran it from the positive terminal on the battery to one of the positive prongs on the back of the headlight and I lit right up. So it's gotta be something to due with lack of power

Or ground.