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Question DetailsAsked on 8/25/2011

My a/c unit thumps like an out of balance clothes dryer. Thoughts?

Trane system. air handler when running at top speed makes whole end of house shake (exact same unit at other end of house is quiet as can be). Also, one motor already burned out (under warranty). Related? Installer's suggested fix: disable top speed. Is this a defective unit? What is the right fix?

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5 Answers


Vibrations come from many things, it would be very hard to know what is causing your vibration without taking a look at it.
Can I ask when was the Trane unit installed. I am a Trane dealer and would at least be able to tell you if the unit is under warranty if you email me the model & serial number.

Answered 9 years ago by cloughman


There are very few moving parts in any air handler. Lowering the speed, if it works, is a temporary solution to a permanent problem. You either have a broken motor bracket or a bad blower wheel. You may have something sucked up into the wheel causing it to be out of balance. The motor itself is seldom cause for a vibration.

Ralph Little

Little Heating & Cooling

Haymarket, Va 20169

Answered 9 years ago by ralph little


Your problem most likely has to do with the blower wheel, bracket or motor housing issue. These components are arranged as follow: the blower wheel sits on the motor shaft; the motor is held in place by a bracket and the housing holds these parts in one place. Any one of these problems would cause an imbalance in the motor's rotations per minute and result in the air-handler unit shaking erratically.

Answered 9 years ago by Stans HVAC


the squirrrel cage has to be replace if it has not damaged your blower motor shaft in that case you have to replace both

ray gonzalez owner of koolray heating and air

Answered 9 years ago by Raymond Gonzalez


Since it is in the Air Handler and the only moving part is th blower wheel, I am going to go on a limb and guess that either a)something is in the blower wheel, which will cause an imbalance or b) the blower wheel has loose blades on the wheel itself or possibly the blower motor bearings are loose. In any of these suituations I would recommend having a certified technician inspecting with the door off and visually inspecting while the unit is running (do not put hands or loose clothing or hair any where near it). Either way if it is an imbalance it is a good idea to change both the blower motor and blower wheel and eliminate any possibility of this happening again. In rare instances the imbalance may also cause the motor bracket to stress, but this is not as common as the blower wheel or motor bearings causing this problem.

The idea of lowering the blower speed is not a permanent fix and may cause issues during winter when your auxillary heat comes on (If you have an electric backup heat), not to mention the problem may get worse and throw a blade which can damage other parts around the blower.


Race City Heating & Air, LLC

Mooresville, NC

Answered 9 years ago by Justin Z

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