Air Return Fan Humming


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Old 07-07-19, 11:55 AM
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Air Return Fan Humming

Recently replaced the condenser fan motor and capacitor in my outdoor central air unit, but now the inside air return fan (at the bottom of my furnace unit) is making a humming/rattling noise. It’s definitely coming from this area and not the return vents/grates. Thoughts to what caused the rattle, or just coincidental timing?
 
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Old 07-07-19, 04:15 PM
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Many furnace blowers have bushings or bearings to support the squirrel cage shaft. If they wear so that there is "slop" in the bushing/bearing, the blower assembly will be noisy and can rattle. The rattle should have nothing to do with the replacement of the condenser fan motor. The condenser fan is outside the house, while the blower (air handler/furnace fan) is inside the house.
 
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Old 07-07-19, 05:48 PM
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Thanks, Bob, that makes sense. I assumed they were unrelated, the timing just concerned me given that it was literally the 2nd time turning it on after swapping the motor that the noise started
 
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Old 07-08-19, 02:22 PM
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Just the close the loop on this: the culprit was the wiring diagram somehow got sucked into the blower. When I spun it by hand to see it the wheel wobbled, it sounded like a playing card in a bicycle spoke. One spin against normal rotation and it popped right out. Weird timing as I hadnít touched the blower compartment it recent weeks
 
 

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