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  1. #1
    Join Date
    Feb 2013
    Location
    Lamar, SC
    Posts
    573

    Condenser Fan Wobble

    Our other tech went on a no cool call and found the condenser fan motor was bad and replaced it with one of truck stock motors. We use Top-Tech motors, a universal replacement sold by the local parts house. We have never had any problems with them, and on this particular replacement the fan shook pretty bad. The homeowner called back and the tech was sent back out, he said he couldn't figure what was wrong and left (did that a lot). They send me out and the customer said, insistently, the the other tech bent the fan blade. I called the owner and told him the whole story, asked if I could swap motors to make sure the new one wasn't defective as the blade looked OK and still had the weights on it. The boss said to just order a new fan blade. Went back out the next day with the new blade and swapped it out, fan still shaking pretty bad. Went ahead and swapped the motor out for another Top-Tech of the same size and RPM, which matched the data plate and still had bad wobble. We ordered a factory spec replacement motor, and installed it and wobble went away. This was a carrier package unit. My question is this. Is it possible that carrier is some how counterbalancing their motors and fan blades so you can only use their parts or is it more likely we had 2 bad NIB replacement motors? Run one of the motors with no blade and it had no wobble.
    "If you've eliminated all other possibilities whatever remains must be the truth."

  2. #2
    Join Date
    Mar 2009
    Location
    Mid-Mo
    Posts
    3,596
    I've seen that happen a lot when someone puts a faster speed motor or a lot larger horsepower motor on it. If you do a 1075 1/3 hp in place of a 1/6 825, it will rock and roll bad. I did this exact thing a couple weeks ago to get us out of a bind.

  3. #3
    Join Date
    Sep 2012
    Location
    New York
    Posts
    175
    I've had that happen to me with some motors, many times the rpm was higher than the oem motor but not by much. Sometimes you can correct by setting the blade a little lower other time I let em "shake"

  4. #4
    Join Date
    Jun 2003
    Location
    Chicago, IL
    Posts
    4,486
    also check to see if the coil is plugged. I've seen that happen a few times. I suspect that the plugged coil makes the fan pull down on the top harder than it was designed for and it starts bouncing.

  5. #5
    Join Date
    May 2011
    Location
    Western, KY
    Posts
    3,226
    On those universal motors they often have two speeds, I found the lower speed is actually the one that usually matches up better and yet almost all the ones I find installed by others are on high... curious.

    The other thing is universal motors are usually longer, sometimes it pushes the blade lower than the... venturi? The part that sticks down around the blade, if the blade drops below this it creates a lot of turbulence. There was actually a run of rheem packs that had this problem straight from the factory and we had to order "dome" tops, instead of the fan grille being the same level as the top it stuck up about an inch or two.

    Then same as others, oversized, dirty coil, watch out for cracks in the fan grille.

  6. #6
    Join Date
    May 2008
    Location
    OKLAHOMA
    Posts
    113
    Did you trim the shaft on the universal motor?

  7. #7
    Join Date
    Sep 2012
    Location
    New York
    Posts
    175
    Good point! Yes sawzaw that shaft down it definitely can cause it to wobble

  8. #8
    Join Date
    Feb 2013
    Location
    Lamar, SC
    Posts
    573
    Didn't cut shaft or have any dirty coils. The factory motor had about a half inch shorter case and about a 2 inch shaft, vs the slightly longer case of the universal and its 4 inch shaft. The blade did end up slightly more centered in the venturi height wise due to the shorter case. Also it was a single speed motor.
    "If you've eliminated all other possibilities whatever remains must be the truth."

  9. #9
    Join Date
    Mar 2007
    Location
    Myrtle Beach, SC
    Posts
    2,919
    I stay away from the top tech motors. Carrier parts is a division of Watsco, who also owns East Coast and Baker Distributors. That is a motor they get cheap. It is the store brand. I have started buying other branded duct ties and capacitors as well as motors because of quality issues.
    JMHO
    Remember, Air Conditioning begins with AIR.

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