Air Conditioner / Thermostat after sitting for 2 years

The "E1 error" - which is common - occurs when there is either a disruption in the communication from one or more of these cables, OR if there is a problem with the Dometic Penguin II AC control board itself.

Suggestion is to UNPLUG and REPLUG the cables 2 or 3 times both at the T-Stat and the A/C end if both ends are plug in type.