Return air question - AC related

[alaxsxaq]

I am replacing all of the return air vents in our house. The vent covers I've seen at Lowes do not have dampers while those that were originally installed had dampers. Should I install units with dampers? At leat in the low position? Also the upper?

Right now, with all of the first floor vents off, we are having problems with air draw in the upstairs bedrooms. Cold air reaches the bedrooms, but there is very slight draw through the returns and the rooms get quite hot. Should things improve with the return air vents in place downstairs?

--Glenn

[SSN596]

Return air grills do not have dampers.

Closing off too many supply registers completely starts to mess with the balance of the system. But definitely do not close off any returns.