so I picked up an ancient Coolmatic by Waeco fridge. It's a little guy. The model is CCF 18. I don't know if it works and would like to try it before investing time and maybe $ in it but am missing the cord. It only has a DC connector on the face plate. It is a rectangular shape with 2 male round pins and a little tab on one of the long sides. Anybody knows the polarity of these cords at the faceplate connector? I imagine / hope it likely is the same for other Waeco fridges. TIA