Blower motor not starting

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  #1  
Old 05-25-19, 01:21 PM
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Blower motor not starting

I have an old Lennox G16 unit (G16Q4/5-125-1). The compressor is fine, but the blower motor tries to but does not start. To simplify things I'm troubleshooting it now in Fan On mode, but it's the same if turning the thermostat to Cool with fan in Auto.

When I turn the fan on, the motor buzzes and tries spinning. Oftentimes it runs for anywhere between a split second and several seconds and cuts out again. 5-10 seconds later it tries again. During this time the blower wheel us still spinning, it does not get a chance to stop until the next 'pulse" which speeds it up again. Occasionally it starts and runs for a minute or 5 and then cuts out again.

This started Thursday but yesterday (Friday) I somehow have been able to start it run for 4-5 hours non-stop until the thermostat turned it off.

The blower wheel spins freely when rotated by hand, with little resistance. I've already replaced the run capacitor and short circuited the door disconnect switch to remove another variable.

It's too old to have a control board so I'm down to these options:
* bad blower motor
* bad connection / bad wire
* blower motor relay?
* what else?
 
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Old 05-25-19, 02:22 PM
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Welcome to the forums.

The first thing you would try is replacing or testing the blower motor capacitor. You replaced the cap and eliminated that problem. That leaves motor replacement time and when you order a new one..... make sure you have the right cap or you'll need to reorder that too.
 
  #3  
Old 06-09-19, 06:49 PM
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It was, indeed, a blower motor. My system uses a resilient ring mounting system so I needed a blower motor with very specific external dimensions to fit my mounting bracket. I tried 3 different motors at Grainger and none fit,but was able to buy one from a local HVAC store that caters to contractors. Got a new correct capacitor to go with it as well. Not only did it start right up, the system is much quieter than it's ever been in our 7 years of living in this house.

Thanks!
 
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Old 06-10-19, 12:31 AM
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Good job. Thanks for letting us know how you made out.
 
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