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Old 08-14-2012, 01:08 PM   #1
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Replacing a furnace blower motor...a few questions

Hi all,

I had my A/C condenser unit replaced two years ago. A few days ago, I noticed the house was a bit warm; turns out the lines had frozen up and the condenser wasn't running. Had a local repair company come out and take a look, and they determined that the furnace blower motor wasn't starting up every time it should have, leading to a lack of air circulation and frozen lines.

The unit was fine for a couple of days, and then the same thing happened. Since then, I've switched the fan to "ON" instead of "AUTO" at the thermostat, and it's continued to run. Curious if this is likely a motor issue, or a capacitor issue? It seems as if the motor will continue to run once it's started, but sometimes won't start up when it should.

If I do end up replacing the motor, I'm curious as to what specs are necessary to look for in a replacement. Current motor is direct drive, 115 volt, 1/5 HP, 1050 RPM, 2 speed, and I need to check the rotation. Are there other specs I need to know? How close does the replacement need to be to these specs (e.g., I assume 1075 RPM is ok, but I'm unsure if it would be ok to install a 3 speed motor, since I'm not seeing any 2 speeds that match the rest of the specs). I'm also seeing permanent split capacitor and shaded pole motors, and I'm not sure if I should be choosing one or the other.

Thanks for any advice.


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Old 08-14-2012, 03:30 PM   #2
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replace or test the capacitor before replacing the motor.

shaded pole motors will be too small for a furnace blower.

three speed replacement motor will be fine.

Have you or the previous tech checked the fan relay or control board whichever you may have?


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Old 08-15-2012, 06:51 AM   #3
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Thanks for the response. When I had the blower unit out yesterday I didn't notice a capacitor; checked the parts list for my furnace and for the motor size I have, there is no capacitor listed - is it possible that there isn't one for some smaller sized motors?

There is a blower relay; unsure whether the technician checked it or not as he did not mention it.
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Old 08-15-2012, 05:59 PM   #4
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look at the motor again. Trace its wires, and see where they go. if there is no capacitor, you could have a shaded pole motor, but they are far and few between.
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