Capacitor Trouble

Thread Starter


Joined Oct 6, 2011
I have a Powermatic PM1200 air filtration unit in my shop. Through a process of elimination I think that there is a problem with the capacitor on its electric motor. while connected to a power source, but not turned on, the motor hums and spins the fan extremely slowly. It appears as though there is some current "leaking" into the motor. Will a bad capacitor cause this problem? A picture of the capacitor is attached. Does anyone know where i can purchase a replacement? Thank you in advance for the help!



Joined Nov 30, 2010
That capacitor is no mystery. In plain English, it is 25 microfarads, 250 volts, approved for direct connection to the power line.

The problem is that shorting the capacitor is not likely to persuade the motor to run. I suspect a short in the motor windings. Check for ohms from each motor lead to the case of the motor.


Joined Jul 17, 2007
Hmm - 25uH; that seems like "start capacitor" size rather than "run capacitor" size. If the cap were bad (open), or the centrifugal switch were "stuck" or just plain open, that would cause the motor to hum but not start. It would overheat pretty quickly, too.