So if it like most range hoods it's simply a weighted flap that gets pushed open when you activate the fan. A motorized flap would be much too complicated for a coach. If you can feel cold air escaping then the flap is likely stuck open.
On my prior class c there were 2 nibs, one on each side, which snapped into indentations on the vent frame to lock it closed. Air pressure when the fan was turned on would then unlock (open) the vent. That vent was an item I had to check before rolling down the road.
US Army (Ret)
2020 Entegra Accolade 37TS
2019 Jeep Grand Cherokee Trailhawk (Toad)
FMCA - F432054
I installed a couple of these on our last RV. You just have to remember to manually open and close them. Since we rarely use the vent fan (with having two fantastic fans) they ended up staying closed all the time after awhile.