Determine if the lights
that are working are 12 volt. This is easily done by removing the cover and looking at the bulb. If the 12 volt lights work when plugged in, but not on the battery when unplugged, then follow the wires from the battery and look for a disconnect switch or fuse. Also, if you have a volt/Ohm meter, (which you should have), you can look at the battery voltage when plugged vs unplugged. Plugged in, it will be over 13 volts, unplugged it will be 12.6 or lower. If it does not rise when plugged in, the battery is not connected to the system, which, again, could be a disconnect switch or fuse. Once you settle the lighting
issue, you can begin to look at the fridge
, which may be a completely different problem. Work on the lights first.