HVAC Blower Fan Noise

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  #1  
Old 07-03-14, 06:42 PM
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HVAC Blower Fan Noise

Furnace/AC blower in our house has started making some horrible noises in the past couple days. I'm guessing the problem is that the squirrel cage fan shaft has come a bit loose and moved too close to the fan housing - making the horrible noise when it comes in contact with the housing.

The noise is usually worse when the fan starts or stops... once running, it may go for 10-15 minutes without any noise, while other times there are only brief moments of silence between the screeching sounds.

Here is a short video clip of the Furnace unit running and making noise...
HVAC blower fan noise - YouTube
I've also attached a photo of the blower assembly after removing the panels from the furnace.

I'm going to try and pull the blower assembly out and see if I can adjust the fan. If you have any other ideas, feel free to share. Thanks.
 
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Old 07-04-14, 07:27 AM
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Try tighting up the motor bracket, you might be able to reach it without taking the blower out.
 
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Old 07-04-14, 10:09 AM
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Last night I removed the blower housing... there was plenty of clearance between the fan and housing, so adjusting the shaft doesn't seem to be the issue. I took the motor and fan cage out and cleaned everything really good. After reinstalling everything, the system ran smooth with no noise for about an hour and then the screeching returned.

I should have tried running the motor without the fan attached to see if the noise might be the bearings in the motor itself. I didn't check to see if the motor has oil ports on it or not. It is 23 years old. It's a GE motor - model 5KCP39KGN691S.

I've included some photos from pulling the assembly, and zoomed in for closeups on the motor... still can't see any oil ports from these photos. I'll probably pull the assembly again today and look closer.
 
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Old 07-04-14, 10:13 AM
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Thanks skaggsje... I really couldn't access the motor in the blower housing without pulling the whole thing first. Not much room in there to work with - but it definitely needed a good cleaning so I'm glad I pulled the whole assembly.
 
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Old 07-04-14, 01:01 PM
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I noticed that the motor bracket is adjustable. Did you check them for tightness?
 
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Old 07-05-14, 11:18 AM
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The motor brackets are tight... everything feels solid, and there is plenty of clearance for the fan. I think it must be the motor bearings/bushings. When giving the fan a good push, it would only turn about one revolution before coming to a stop... maybe 1.5 revolutions. I would think the motor should spin more freely than that?

I pulled the blower housing again this morning - and I could not find anything that looks like an oil port. So I'm guessing this motor uses a sealed system. Looks like it is time to order a new motor.

I've attached a better close up of the top of the motor in the housing... in case someone can see something I am missing. Thanks for the help.
 
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Old 07-09-14, 10:16 PM
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AC is working smooth and silent once again...

Ordered the replacement motor and new capacitor on Monday (July 7th, 2014) and received it on Wednesday. Installed it that afternoon - I had to cut the old wiring harness from the old motor and install it on the new one. Also reused the old motor mounting bracket successfully on the new motor. After installing the new motor in the blower housing, the fan spun very freely - spinning for several revolutions before slowing down (unlike the old one, it barely went once around before stopping). Installation went without a hitch and now the AC system is running smoothly again with the blower quietly pushing the air.

The replacement motor, capacitor and shipping came to about $240... saving me a lot of money compared to the $500-650 rough estimate I received.
 
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Old 07-13-14, 09:06 AM
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Same issue problem husband

Hi, It's great you are not having the noise issue anymore. My Am Standard Heat Pump is doing the same thing and I had the tech out yesterday.

He diagnosed the problem as bearings that have lost their lubrication. Can't be replaced so we need a new motor.

My problem is my husband is skeptical since the noise is not that bad in the winter.

Could the noise be worse because it runs faster in the summer? Is that what the 2 stage motor does?

Thank you,

Maria
 
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