Help on dometic Refrigerator issue

[bardave]

taking a chance that someone will Know what the problem is and may respond.

my Dometic Refrigerator model NDR 1292, serial #
54200034, WILL NOT operate on gas when not plugged in
to power.

I can plug it in to power .... it operates on electric
....pushing the AES button, it goes to gas...I can
push the AES button back and forth between gas and
electric and it switches from electric to gas OK. I
can hear the gas operating in the backside of the
fridge.

While running on gas....I can unplug the power cord,
and the gas goes off, the refrigerator quits
working...

I have fully charged batteries

any clues as to why this happens and how I can fix it