the manual says
Push the source button several times, as illustrated. Push until the desired source
(A, ‘auto’) is selected and displayed.
If the engine is running, DC mode will be selected and displayed.
If the engine is not running, and 120 volts AC is available to the refrigerator, AC mode will be
selected and displayed.
If the engine is not running, and 120 volts AC is NOT available to the refrigerator, gas mode
will be selected and displayed
the manual says
These models have 2 connection points to prevent the battery from being discharged by the
refrigerator when the engine is not running
there is a connection on the back that senses the engine running the manual shows
D+ signal orange wire, + when engine runs
the current draw when running on 12v is above 17 amps
