Last year I was testing the car socket with a multi-meter to see if the 12vDC permanent live feed was working. I thought it wasn't, although the fridge seems to keep cool when towing and switched to the right setting.
This diagram was the one I worked from and I was very puzzled. I put this all down the the way car battery charging has changed.
Now I see that the wiring diagram is as viewed from the rear!!!! Dooh!
Alan