How do I know if blower wheal is unbalanced?

Old 12-09-10, 02:40 PM
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How do I know if blower wheel is unbalanced?

My furnace is making some weak rumbling sounds when the blower motor is on. I can not make out if its the 1) bearing of direct drive motor or its coming from the combustion chamber above the blower compartment. This noise stops completely when the furnace shuts off. The blower motor/cage runs very smooth if I spin it by hand.

Without removing the cage, I have checked the fins on the wheel - they are dirty (i got dirt on my fingers) but not clogged; i change filters regularly. There is axial play in the motor shaft (is that normal?). How do I know if the blower wheel is unbalanced w/o taking the motor/wheel assembly out. I have watched it spin very carefully and dont see any axial movement or wobble.

Also, there is a humming sound that comes from the motor/cage. This sound stops if I push the blower motor housing up by pressure. I have checked the nuts that hold the blower motor assembly. They are tight. Could this be caused by motor grumetts (sp?) being worn out?


Last edited by vkaura; 12-09-10 at 02:46 PM. Reason: correct mistakes
Old 12-09-10, 04:32 PM
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You need to remove the fan assembly to inspect what's happening. Any of the things you suggest could be possibilities, but you need to do more work to figure out what's the problem.

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