on my dometic, i have to switch to auto and it will select elec first and if that isn't available, it will switch to gas.
in the back of the frig, there is an A/C power cord, make sure it is plugged in and the breakers aren't tripped. if it isn't getting A/C, it will assume no shore power and switch to gas. the control circuits are all DC.
My refrigerator (DM2652) quit cooling less than a month after I got the trailer. The auto light stays on no matter what since it is 12V. I found the GFI had tripped and no 110V was even getting to the unit. When I did reset the GFI I still thought the unit was not working because the compressor would not kick on immediately. Be patient. For some reason it does not come on immediately. Give it about an hour and you will know if the unit is cooling properly or not. It takes several hours to get to the proper operating temperature.
There is no compressor on a rv fridge, it will take at least 8 to 12 hours before you notice it cooling, but no compressor, you might have a cooling fan in the back.
__________________
The Family Truckster Team:
Michael & Belinda
That tells me why whatever kicked on doesn't kick on immediately. Our old trailers fridge always made a sound to indicate it was running when you plugged in the shoreline without having to go around and look at whatever lights were...or werent...working.