Noise from Forced Warm Air Furnace


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Old 09-27-13, 07:02 AM
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Noise from Forced Warm Air Furnace

This may be a little vague but here is my question. When the furnace comes on in the morning, from not being on all night, when the motor starts there is a vibrating sound that lasts about 10 seconds. This will not happen again all day until the first start-up in the morning. I thought it might be the motor starting capacitor, which I replaced and it was not that. Any wild guesses? Thanks in advance.
 
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Old 09-27-13, 10:13 AM
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You may have to open the blower service door and start it up while you are there. It could be a motor, a belt or a blower wheel bearing issue.

Once you open the service door...you'll need to hold the safety interlock switch in for blower to run.
 
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Old 09-27-13, 02:15 PM
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I've done that a couple of times. Remember, it only happens once a day for about 10 seconds. It works fine the rest of the day until the next morning. I guess I'll have to wait for it to get worse to detect the problem. Thanks for your thoughts, PJmax.
 
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Old 09-27-13, 07:15 PM
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Is the blower belt driven ? Check or replace the belt first.

Try turning the blower slowly by hand and listen for noise or feel for something rubbing.
Make sure service switch is off to the furnace before putting hands in blower area.
 
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Old 09-28-13, 05:39 AM
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It's a direct drive blower and I've tried turning it by hand....no noises. The mystery is that it only happens when the blower comes on after the furnace been off overnight and only for those few seconds.
 
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Old 09-28-13, 08:48 AM
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The only thing I can think of is that the lubricant in the motor bearings settles out or hardens.
It'll probably come down to replacing the blower motor at some point. Hopefully it won't fail in the middle of the night.
 
 

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