Your fridge probably does not have a 12 volt function....that type of fridge is usually restricted to tent campers. Now that being said, your fridge does require 12 volts to operate the circuit board.
If your fridge is on automatic, once you unplug your shore power, the fridge will automatically switch to propane...as long as your tank valves are open. That is usually the only option that you have going down the road.
Now if you have a true 3 way fridge (12 volt, 120 volt, and propane), please disregard my above statements.
Chap , DW Joy, and Fur Baby Sango
2006 Ford F150 Super Cab 4x4
2008 Surveyor 263