Fridge has been fixed. Car was checked out by an auto electrician. Car 12v supply was OK. He then had a quick look at fridge electronics. The fridge’s PCB had a burnt out section! Packed up the caravan and took it to a fridge repair business in Mt Isa. They fortunately had a replacement, albeit 2nd hand board. The board was fitted, tested and for about $400 all up, have a fridge which works on 12v again. It seems the onboard PCB 12v fuse was not correctly seated and one of the legs only touching it’s connecting point. No doubt with bumps along the road, there was a spark which burnt out the board.