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Ivylog's avatar
Ivylog
Explorer III
Aug 07, 2014

Replacing fan motor in roof AC

Several years ago the fan started to slow down after several hour of use. Tried oiling the bushings which seemed to help but recently it's gotten so bad that after 15 minutes the motor slows down and even stops. Decide to remove the motor but it's a heck of a project because of all the sheet metal that was not designed to be removed. Even though the motor shaft was centered in a hole in the sheet metal, the fan was very close to the bottom so I decided to raise up that end of the motor. Put 3/16th of spacers under the motor mount and now the motor turns freely. Apparently over time and bouncing down the road the bottom pan of the AC has bent upward and the fan was rubbing on it. I now have a well oiled fan motor and fortunately I had not bought the replacement motor I'd found on Ebay.
Class A

8 Replies

  • Ivylog's avatar
    Ivylog
    Explorer III
    Aug 08, 2014
    When I swapped out the run capacitor from one of my other Dometic 630515 units is when I figured out that my problem one did not turn as freely.
  • Golden_HVAC's avatar
    Golden_HVAC
    Explorer
    Aug 07, 2014
    Ivylog wrote:
    When looking for a fan motor I came across this kit but I'm not sure if it's for the fan or the compressor... leaning towards the compressor as it looks larger than the fan motor mounts.


    Judging by the size of the locknuts, I am guessing it fits the fan motor. The compressor should be held down by a 3/8" or so size bolt. And the compressor should not be mounted firmly to the metal base, or it will transmit more vibrations into the base metal.

    For a slow fan motor, you already found out it is rubbing, and is your cause. Many times a slow fan motor is bad bearings or a failed run capacitor. A run capacitor will run about $8 wholesale and typically is 4 or 5 MFD. Some might be as high as 7.5 or 10 MFD.

    Fred.
  • Ivylog's avatar
    Ivylog
    Explorer III
    Aug 07, 2014
    When looking for a fan motor I came across this kit but I'm not sure if it's for the fan or the compressor... leaning towards the compressor as it looks larger than the fan motor mounts.
  • ScottG's avatar
    ScottG
    Nomad
    Aug 07, 2014
    Ivylog wrote:
    There are four rubber bushings, two on each end of the motor. There was very little movement and even lifting up on the fan I could not get 3/16th movement at the fan.


    I wonder if they need to be replaced?
    Mine has all kinds of movement.
  • Ivylog's avatar
    Ivylog
    Explorer III
    Aug 07, 2014
    There are four rubber bushings, two on each end of the motor. There was very little movement and even lifting up on the fan I could not get 3/16th movement at the fan.
  • wa8yxm's avatar
    wa8yxm
    Explorer III
    Aug 07, 2014
    More than likely there is a small rubber "Bushing" around the motor that has wore out a bit allowing it to drop down.. Good job on fixing it though.

    No matter what the cause.. Good job on fixing it.
  • Ivylog's avatar
    Ivylog
    Explorer III
    Aug 07, 2014
    It's a squirrel cage blower and I could not hear it rubbing, even turning the shaft by hand. The other two units will keep turning for several turns when spun while this one would stop in less than a turn. It's the front unit and I guess it takes more bouncing than the other two???
  • ScottG's avatar
    ScottG
    Nomad
    Aug 07, 2014
    Good to know! It sounds like your lucky the fan blades didn't break hitting like that.

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