Pump motor hums but capacitor OK and impeller spins freely

I have a Hayward Super Pump with AO Smith 1hp motor.  Had a problem at the beginning of the season where it just hummed but wouldn’t start, so I checked the blogs and was able to get it going by manually freeing up the impeller.  Ran all season without a problem, then it just stopped again the other day.  I checked the impeller at one end and the motor shaft at the other, and was able to move everything freely.  Changed the start capacitor, even though the old one still showed it was OK with the meter.  Still just getting the hum, and can’t find any other suggestions in the blogs.  I’m OK with buying a new motor if necessary, but feels to me like this one may be OK since the typical failure modes aren’t the problem.  Any suggestions?  If I do need a new motor, do I just need the motor and a new shaft seal, or any other parts recommended as well?

Hello Mark - The most common cause of a motor humming is a bad capacitor. Since that is not the problem, it’s probably a bad phase winding. In that case, you’d replace the pump motor.

Check out our guide titled “How To Use a Multimeter to Test a Pool Pump Motor - Winding Resistance