Not sure about your Marquis, but on mine and some others the controller is in a “hidden” bay where the waste tanks and some Aladdin modules are. The bay has no obvious latch and looks like just a plain side panel. It’s immediately forward of the curbside rear wheels and it has two swing/draw latches along its underside edge... you may have to get on hands and knees to see them. The door swings up, and on mine the solar unit is on the upper wall to my left, the white box in the photo. It’s a pass thru bay I guess, but the street side is blocked by the wet bay panel.
As noted, yours is a much different coach, but it’s worth a look.
Joel
