Fixing return ac vents

[Chris K]

2021 3120rl
I am looking to get my ac systems tightened up. I pulled the return covers inside and the tape job from the factory needs to be redone. I will likely add some blocking before taping to prevent future issues.
My concern is that I don't want to assume and completely seal off the 3 sides of the return that face away from the middle of the camper. I can't tell what should be completely sealed and what should be left open for return air.
Any advice?
Thanks

[Foldbak]

Common problem. You need to remove the vent covers and flatten or replace the tape. That simple.

[Daryles]

Take a sharpie and trace a line around the inside of the return plastic trim. Remove the trim and cut off the excess blocking the return vent. Tape it sealed.
Inside the return duct, one side should be open for the return air to go through the cooling coils.
Seal everything else. I could put three fingers through this hole. This allowed hot attic air to get into the return duct (before and after pictures).
As for the vents, remove the vent, trim the flange (neck) that protrudes up into the duct so it's flush with the styrofoam insulation inside the duct.

All of this will help improve airflow.