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Furnace Blower Motor fan hums but wont start until I turn it by hand, then it runs fine. What should I check?

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    What make and model is said furnace? – ThreePhaseEel Nov 5 '19 at 5:32
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    A bad capacitor is most likely Capacitor give the motor an extra kick of power at start up. Edit in the make and model of your unit and a picture of the inside workings – Kris Nov 5 '19 at 14:15
  • @kris, this is the most likely the answer the op needs. Many times the cap body looks bulged when they are bad. With the cap out of circuit a ohm meter can be used to see if the cap is working. First short the cap just in case it still has a charge you don’t want to damage your meter, Ohms function across the cap and the reading should be charging up. If shorted or no change the cap is bad. – Ed Beal Nov 5 '19 at 15:24
  • @EdBeal I agree. We would need to see the blower motor to ascertain if it has an external capacitor some do some don’t. – Kris Nov 6 '19 at 3:17
  • Actually from experience with this exact problem, it might not be the capacitor. A broken wire in the start winding will also create the same effect. What I did was removed the blower assembly and took it to a motor rebuild shop. They diagnosed it , replaced the motor with the correct capacitor and cleaned it all up like new for around $110. The whole project took 2.5 hrs and is even quieter than before. – user68386 Nov 8 '19 at 0:47
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Before I would check for any of the potential electrical issues I would try lubricating the motor shaft. Shut off the power to the furnace. Gain access to the fan and motor. Spray a small amount of lubricant (slick50,chain lube, etc) almost any light oil will work, on the shaft where it exits the motor. Some models may even have been equipped with a small oil port from the factory. You may have access to the opposite end depending on the design. Spin the fan by hand a few times. Apply a small amount of oil again. Wipe off any excess, reassemble and see if the fan starts.

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