Davinger - that's right on your fridge. Typically they are 2 way fridges these days if norcold or Dometic.
The 12 volt required during the propane setting is used for controlling the electronics (igniter, etc). A 500 milliamp draw is typical.
There are 3 way fridges that will do a true 12 volt (without propane) cycle but the amp draw is much higher on that setting. Lots of folks ended up with dead batteries in the "12 volt only" setting. I'll admit that I would feel a bit safer driving down the highway with the propane off completely at the tank, but haven't had any issues on propane.
History:'05 Concord, '08 View, '05 Chinook, '01 Jamboree 24D, '78 Apache Popup, 81 Komfort Tlr,
84 Mazda B2000 'w canopy,Tent from wedding in '96