[jasin1]

when they were building the trailer they likely just ran one wire long enough to reach the refrigerator and furnace instead of a home run for each back to the panel….used one 12 volt fuse……left enough slack to pull the wire into the furnace junction box..cut it and connect the furnace to the pos and neg wires…end of wire connected to refrigerator.
….In some parts of the country or with some peoples camping styles they may never even use the furnace so nuisance blown fuses aren’t as likely and the wire and fuse are sized to handle both loads…they probably saved $1.67 doing it that way lol