Like Ron says, make sure you have good air flow across the refrigerator compressor coils and the coils are cleaned regularly and the fan works to move air across the heat exchanger.I turn up the fridge temperature at night since it won't be opened, and I leave the door open under the sink where the fridge compressor moves heat to the fridge.
There is a "plug in" smart controller that will fit most of the standard refrigerators and freezers that does some neat stuff with energy conservation. When you are on the engine or external power (higher voltage) the smart controller runs the compressor at full speed and lowers the temperature in the refrigerator, thereby "storing cold" in the items in the refrigerator. Then when it senses the external power is no longer available it goes into a "conserve energy" mode and raises the temp to a higher (but still safe) temp.