Hi,
My central air unit is on the 3rd floor. When it's on, the air flow on the 3rd is tremendous and it becomes cold in a second. At the same time, the air is barely coming out on the 2nd and the 1st floors. The ducts are old, but I inspected the parts that are accessible and they seem to be intact. What could be the problem here and what should I try next?
Many thanks in advance,
Aaron