in many cases, the 12v mode, was travel mode, and good only for trying to lessen heat gain
it would not cool a hot fridge, the DC element was less wattage than the AC element, but plenty good for running down the battery IF you made a mistake
besides if you try this
the parts you have to change, are all the control parts, boards everything, maybe even the wiring harnes, as the (2) fridges probably have different wiring
IF you want to swap parts
then i would suggest swapping the old cooling unit into the new fridge
aka then there are no wires or control changes to worry about
