2nd AC unit - outside odors being pulled in
We have a 2020 Fredom Express LE with a second AC unit in the main bedroom area. We've found that when it is on it pulls in outside odors quite proliferically. I normally wouldn't mind, but when at a rather tightly packed campsite and people using a lot of lighter fluid, it can be quite noxious. It's a dometic unit that doesn't have the option to pull outside air (full recirc-type). When I examined the unit, it seems to not have a good and solid seal to the roof. in fact the metal plate that is bolted to the roof does have some up and down movement.
I used some incense around the base of the unit and sure enough the smoke is sucked into the unit quite readily. I attempted to use some of that aluminized hvac tape to seal around the base of the unit as well as any seams that appear to have air infiltrations as well, but our past camping trip had the same issue. I'm guessing the tape lost it's adhesion due to the movement during towing.
I took it to the dealer before trying any self-repairs for the issue and of course they couldn't find any issue. The unit is now out of the 1 year warranty as well.
Should some kind of butyl tape be used underneath the whole unit? I couldn't find whether that should be the case or not. I'm pretty handy so not afraid to remove the unit in full to figure out what's going on or to resolve it more appropriately.