Changed Condensor Fan motor outside , Not it's making a rumbling noise

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Old 10-08-13, 10:26 AM
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Changed Condensor Fan motor outside , Now it's making a rumbling noise

So to make a short story quick, My AC in the house stopped working It was blowing hot air, The fan was making a buzzing noise. After some research I changed capacitor ( wasn't the problem) Then I changed the motor. Wasn't too difficult but it was my first time doing it, so I am not a professional at all but somewhat handy. Anyways now the AC runs fine, fan blows and there is cold air.

But it's making a louder then normal rambling noise, I tightened all the screws. The old motor had a short shaft and the blade was about a inch and a half away from the motor. This motor has a long shaft maybe 8 inches or so, I put the blades roughly in the same position. But there is an excess shaft, Is that causing the rambling noise? Maybe the motor is shaking? The fan blades don't look bent at all, Maybe not balanced?, I could be wrong? Would a tiny slight bent or imbalance cause all that noise? How do I check if my blades are balanced or bent?

Can I cut the excess shaft off of the motor? Would that help?

PS: I don't think it's the condenser as it was making the same noise with it off. and the Fan blades aren't hitting anything.

I included a video of my exact AC unit, I posted it on youtube.

Any help is appreciated. Thank you

http://www.youtube.com/watch?v=jNJZtuKrUC0&feature=em-upload_owner
 

Last edited by mg0698; 10-08-13 at 11:08 AM.
  #2  
Old 10-08-13, 10:55 AM
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Welcome to the forums.

You can cut off the extra shaft length but that probably isn't causing the problem.

More important than the fan being the same distance from the motor ...... does the fan end up in the same place inside the unit. The height in the opening is important.

The only way to check for a blade being bent is to use something like a strait edge that you can measure the difference from it to each blade. It's pretty difficult to just eyeball it. A bent fan blade is the usual cause of excessive vibration.
 
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Old 10-08-13, 11:15 AM
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Thank you for the Warm Welcome !


Are you taking about the fan blade or the motor?

The fan blade is roughly about a inch or 2 lower then it was before. The motor is roughly in the same position.

How much of a problem is this rambling noise? I have left the unit on even with the noise, I live in S. FL and it's really hot.
 
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Old 10-08-13, 12:08 PM
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Pete was referring to the vertical positioning of the fan blade assembly. It should be positioned in approximately the same location (height) as the original fan blade assembly.

The rumbling noise is likely due to an imbalance of the fan assembly. An imbalance will cause extra wear/tear on the motor bearings (or bushings if a cheaper motor). In other words, the imbalance will likely cause the motor to need to be replaced sooner than it otherwise would be.
 
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Old 10-08-13, 12:15 PM
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The shaft doesn't need to be cut off. It is very important that the distance between the blade and the new motor housing be the same distance as it was on the original. In the video you posted it appears there is a big imbalance in the blade as it is spinning. There is a metallic sound like the tips of the blades are barely hitting something.
 
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Old 10-08-13, 12:45 PM
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I never worry about the distance from the motor because it can vary. I mark the blade at the point that it lines up with the bottom of the shroud, with a pencil.
 
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Old 10-09-13, 06:56 AM
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Is there any way to re-balance it? And thank you all for the advice so far.
 
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Old 10-09-13, 08:40 AM
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Did you check to see if all of the fan blades are the same height? Pete told you how to check it:

"The only way to check for a blade being bent is to use something like a strait edge that you can measure the difference from it to each blade. It's pretty difficult to just eyeball it. A bent fan blade is the usual cause of excessive vibration."

With the unit turned off, drop a ruler through the fan grill and measure the distance to a position on one of the fan blades. Gently rotate the fan by hand (holding the ruler in the same position) and see if the other blades are the same distance. If not, gently bend the blade that is off (either high or low) so that it's the same distance as the rest of the blades. Now, all the blades will be "level" and the vibration should be reduced or eliminated.
 
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Old 10-09-13, 08:45 AM
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ok Thank you I did that, And I moved the blades about a inch up so it was where the blades were before. Still making the noise .

I'm gonna post another video .
 
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Old 10-09-13, 08:53 AM
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I think you misunderstood what Pete and I were trying to tell you. While it is important that the fan assembly be positioned vertically where it originally was, that will primarily ensure that the airflow through the condenser coil is maximized.

As for the imbalance, the important thing is that all of the fan blades (I assume you have either 3 or 4 blades on the fan) are at the same height (level). That's why we suggested that you measure the height of each blade to ensure that they're all the same. If they're not, gently bend one (or two) so that they are at the same height. It doesn't matter what reference point you use to measure the height, so long as you use the same reference to measure all of the fan blades.
 
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Old 10-09-13, 09:21 AM
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one blade was slightly higher then the other but not by much I tried to bend it back to the best of my ability still didn't help, Maybe you guys see something I don't? Here is the the motor running upside down.




http://www.youtube.com/watch?v=Ex-NoHatruo
 
  #12  
Old 10-09-13, 09:58 AM
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There is a definite metallic sound. Try this. Remove the fan assembly from the motor and run the motor (without the fan). Does it still have a similar metallic sound, or does it now sound relatively quiet?
 
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Old 10-09-13, 08:04 PM
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This should determine if it's the fan blade or if I mounted on the motor incorrectly right? Should I have put on rubber washers or some sort of pad to stop the vibration? Would that help?

Thank you
 
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Old 10-10-13, 05:48 AM
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In the videos you have posted, there is a "metallic" sound, like metal hitting metal (firedawgsatx noted this as well). Since you say that the blades look okay, I'm wondering if the metallic sound is coming from something else (either the fan motor itself, or the compressor). That's why I asked you to try running it without the fan blades. I would be concerned about what is causing the metallic sound.

If the noise goes away without the fan blades attached, then there is something wrong with the fan assembly. However, if the noise doesn't go away without the fan, then you need to look further into the source of the noise. If the noise remains without the fan, try disconnecting the fan motor (don't run the system for any length of time without the fan operating). If the noise is gone, then the fan motor is bad. If the noise remains, then it would appear that you may have a problem with the compressor, and it may be time to call a technician.
 
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Old 10-10-13, 08:13 AM
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ok Thank you again. I'll do that.
 
 

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