I just replaced the a/c unit on my 2015 Prime Time Crusader 315rst. The replacement unit is a new Dometic 15k Brisk Air 2 Evolution. Since my 5th wheel has a fully ducted a/c and furnace, I don’t have a non-ducted unit in the ceiling. Just have a thermostat on the wall and duct vents throughout the camper. My original thermostat gives me an E1 code, meaning that it is not communicating with the roof unit. I think I may need to replace the thermostat with a newer one that has an RJ11 plug and then run the phone wire up to the roof unit and plug it into the RJ11 port on the control box. Am I on the right track or is there an easier and better solution?