[jcurtis934]

You can't without dropping individual panels of the inside ceiling! What you can do is take covers off the inside ac out vents and take a picture looking both ways to see what the condition of both ducts are. To remove a cover, insert a small flat bladed screwdriver under the cover nearby where you see an indent in the cover. There are three of these plies and you will hear it click when you pry it apart at each spot or maybe not. Even if you find something, it will be a major project to pull down the ceiling to fix something.