Cold Air Return issue

ra1185DIY

I have a 2 story house with a basement. My upstairs always seems to be colder than the downstair areas. Last year we had a new high efficient furnace and AC installed. Immediatly it started short cycling since it wasn't getting enough cold air. The was no way to install additional cold air returns upstairs so the installer installed a larger cold air return plenum along with another cold air return in the basement. That did stop the short cycling but my top level is still cold, Someone told me to block off the new cold air return that was installed in the basement since its pulling all the air downstairs. Not sure what to do....Help...Thank You

beenthere

Did they put the same size in as the old one was. Its probably over sized. And the duct work is under sized. And causing the air to be forced out the shortest supply runs which is of course the first floor ones. And any ones in the basement.

Either you need to get a return up there. or more supplies up there.

Closing off that new return. Will probably harm your new furnace.