I have a 1995 manufactured Goodman GMPN gas furnace to which I subsequently added an A/C unit.
My problem is that when the blower fan comes on it makes a racket. The blower blade spins with no noise when manually turned. The sound is tinny as if it is resonating with the sheet metal in the chamber where the return air enters.
I thought of replacing the blower -- about $200 for a 3/4 hp 3 speed motor -- but was wondering if there is any other cause for this noise problem and how can I verify that it is a blower problem??