nayther wrote:
...Took some foil tape and sealed between the two plenums and it helped A LOT!
I did the same thing, not knowing what I was doing, just made obvious sense to do it since air cold air was being sucked right back into the AC and not forced out into the living space. I used aluminum stove pipe tape (extremely sticky and meant to be used on gas water heater or gas furnace flue pipes). So the tape will never be a problem. Once all the holes were plugged, BIG, BIG change in air output!
Good tip here! Easy fix and costs nothing but some tape.