Yes, the cowling that I refer to is the "trim ring" holding the filter BUT on a number of other dometics, it houses the control panel. I am still suspicious of the "combination" of manual thermostat with a "new AC" as dometic went to a digital controller / thermostat a while ago.
I think you really need to find out what model of AC was installed as that will likely help with understanding what controller it is equipment with.
Actually, back up a bit.
What equipment did they actually install??? What thermostat was originally there?
