Furnace Blower Makes Humming Sounds at Low Speeds


When my house is warm enough so that my furnace runs at one of the lower speeds and the burner isn’t on, the blower motor makes a humming noise and seems to slow to a crawl. Might the problem be a bad capacitor, or what else could be the problem?

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ASHLEY 7 months 2 Answers 354 views 0


Answers ( 2 )

  1. Ashley,

    What you are experiencing sounds like a “variable speed” fan motor. I will speed up slowly and slow down slowly. If your fan switch is set to “on” at the thermostat it will cause the fan to run continuously. Ensure the fan is set to “auto”. If the system is heating properly, it could be the design of the system.

  2. The capacitor helps the motor start, if the motor slows to a crawl, it likely is drawing very high amperage, it will stop soon. The motor will likely need replacing, the capacitor should be replaced at the same time. Make sure you have a clean furnace filter so that the motor isn’t working over to hard pushing air. Checking the amperage draw will tell you for sure, if its higher than the rating plate on the motor, the motor should be replaced.

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