Noisy AC cooling fan motor when it stops

Old 05-22-12, 06:22 PM
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Noisy AC cooling fan motor when it stops

Two years ago I replaced the cooling fan motor on my central air conditioining unit as it was bad. The new fan works well and is not noisy when it is running but when it shuts off it makes a very very loud bang which seems to be louder this season than last. I have asked many people including a refrigeration service technician and no one has offered any ideas. The fan stops fairly quickly after the bang. The fan blades turn freely when the motor is off.

I should have added is this a serious problem where I should replace this motor?

Last edited by hvactechfw; 05-22-12 at 06:53 PM.
Old 05-22-12, 07:01 PM
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Are you SURE it is the fan motor? Maybe it is the blade, check it over on both sides. Maybe it is the compressor? Noises are impossible to daignose over the internet. It sounds like you have some more diag to do.
Old 05-23-12, 10:14 AM
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Just like the last feller... are you sure it's the motor?

My ducts used to make noise if it didn't have all the vents open and the sudden change in the duct work when the pressure drops as the fan shuts down would make some very odd noises, every once in a while, a "bang".

Try opening all you vents wide open if they aren't already and see if that helps.

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