You do not state year or Model number. BUT, E1 on a Dometic means loss of communication. That means that somewhere between The wall tstat and Zone 1 the COM cable that looks like a flat phone cord has a problem. MOST common problem IF you have the Lo Profile Penguin Models is corrosion in the evaporator area where the COM cables connect to the Wall tstat and Zone 1 and Zone 2. Since you have a 5th wheel Zone 1 is usually the Living room unit and Zone 2 is the Bedroom unit, but it is NOT a hard rule. Do you have the older style 14 inch square inside on the ceiling the access panel with the Air filter? If so, you can access the Phone type connectors and unplug and check for rusted pins. IF NOT, you have to go on top and remove the AC covers and the Plastic or styrofoam Evap cover to access those connections. This is usually the cause of intermittant connections. Fix is to cut off the corroded plugs and install new plugs. Doug
