My problem with our new 2014 Bighorn was not exactly like yours, but this may give you an idea. To make a long story short, when you turned on the inside panel switch for the 120v electric water heater, the current went to the YETTI cold weather heating pads on the holding tanks. When you turned on the switch for the YETTI heating pads, the electric water heater was powered up. In behind the switch panel on the inside of the 5er there are five relays that are connected with color coded wires. Two of the relays had the wrong color wires on them. I swapped out the two wires and put them with their corresponding colored wires and everything works as it should. Good luck and keep us informed.
Lakeside