I have a Trane XR80 furnace, circa 2002. The blower motor died today.
I purchased a new motor and replaced it. Started the A/C and it blows great, but now on the first floor above the furnace I have what sounds like the washing machine on spin cycle.
I looked in and spun it and it doesn't seem to be wobbling or hitting anything. The set screw is tight, I even went around the furnace and tightened every screw.
Any ideas on what to look for or how to fix? It seems out of balance, but everything went in the way it came out
Best Answer
If the motor uses a belt to connect to the fan it is possible that:
If the fan rotors directly mount on the motor shaft it is possible:
Sometimes there are two motor shafts, one on each side of the motor. Two separate fan rotors would be mounted on the two shafts. The two rotors in such case may have been originally balanced by adding small clip on weights to the blades of the fans. If they were re-assembled to the new motor with a different rotated offset from one another than the original then the balance weights may now be creating an imbalance.
If the fan rotor is a type that has a single mount to the motor shaft it is common that this mount is to a centered (from side to side) support plate on the rotor assembly. It is possible that the plate is made of cheap thin metal and can be bent just enough that the fan rotor gets a run out variation as it makes each turn. Even a small apparent run out of say an eighth inch or so can create quite a vibration at full speed.