The motor hums, but will not turn over

by Jim
(Aliso Viejo, CA)

I have an old Rolair compressor. When I plug it in and turn the switch on the motor hums, but will not turn over. This happens regardless of how much pressure is in the tank.





Bill says...

I'd start with seeing if the capacitor is working. It may not be supplying enough power surge to get the motor going, yet the motor keeps trying, and the humming you hear is often the result.

Cheers,

Bill

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The motor hums, but will not turn over

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Nov 16, 2011
 8 Gallon Campbell Hausfield HUMMMM!!!
by: Joe (Canada)

Hi All,

Just tell let you all. I bought the above compressor and it had a load electrically humming sound when trying the compressor on. When removing the cover and turn on off on the compressor, you could tell the fan would turn just a little bit. No questions to me when I saw that the Piston was seized. Open it up and sure enough the Piston was seized, the oil was cream biege color and water was floating on top it. I took the piston out of the cyclinder head, cleaned both piston and cyclinder head with Emery Cloth sand paper (honing tool would be better but would of cost me than I paid for the compressor). I also the valve plate with a dremal wire wheel. Re-assemble everything put in new oil and VOILA!!! Works like a new one and I just paid $20. dollars for it.

Thanks
Joe
Sep 18, 2011
 huuuummmmmmmmmmmmm
by: rob

I HAVE A BRAND NEW BALBOR 3 HP SINGLE PAHESE AIRCOMRESSOR MOTOR AND ALL I GET IS HUMMMMMMMM WITH OR WITHOUT A LOAD ON IT ALSO YOU CAN TURN THE MOTOR FREELY BY HAND BUT WHEN YOU TRY TO BHELP BOOST IT WHEN POWER IS APPLIED ITS LIKE THE MOTOR IS FROZE UP WTH ?????? HELP PLEASE

__________________

If your power supply is sufficient and clean, then you likely have a start capacitor or a short inside the motor.
May 09, 2011
 Check the capacitor
by: iceqube

You probably need a new capacitor. Disconnect the cap and with an om meter connected across the leads you should see a charge and then on ur meter and then it will stop as the cap charges. If you see no charging most likely the cap is open.
Jul 19, 2010
 Compressor will not run
by: Ron

I have the same problem with my Coleman air compressor. However, I just took the capacitor in and tested "good." Any other possibilities?

Tx - Ron

______________________
The motor hums because it cannot rotate. It cannot rotate because it cannot get enough "juice" to fire up, or something is stopping it from rotating.

The something is often the load. Check out the Unloader Valve page for details about what they are, and how, when they don't work, they can stall a compressor motor.

B.
Jun 28, 2010
 capacitor
by: Anonymous

dont test it with your tongue. If its gone bad, it will not have any power in it. If it is good It has power stored in it like a quick surge battery.

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Don't test it with your tonque???? Who'd have thought anyone would? Good, if somewhat unusualadvice.

Bill
Apr 05, 2010
 Hum but no air
by: Jerry

I have a Rol-Air PMP11MK200FI and the same thing happens to me. I turn it on and it hums. Eventually it trips the circuit breaker.

Is it probably the capacitor?

Thanks!

Jerry R
Mar 08, 2010
 Capacitor
by: Mitch P

I have the same problem with a speedaire compressor. Motor hums or buzzes and won't turn over and start. How exactly do you test the capacitor?

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