There are different modes for fridges. Some are two-way, generally meaning either propane or 110 volt. In the latter case, this means being plugged in somewhere (shore power, generator). Others are three-way: propane, 110 volt or 12 volt
. I'm not sure how North American three-ways work, but on our European Dometic three-way, the 12 volt
must come from the tow vehicle, not from the RV.
Many modern units require a smidgen of 12-volt electricity to operate on propane. (It's just to operate the control system, not to participate directly in cooling.) Note that this 12 volt
supply can come from the RV.