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Electric Power & Utilities/Motor makes noise and overheats after being dropped


QUESTION: Hi Charles. I have a single phase 110/220 1.5 HP Siemens motor. It was accidentally dropped and the run capacitor as well as the frame were damaged, also the rotor rubbed a little with the stator. Neither the start capacitor nor the centrifugal switch show apparent damage. After changing the run capacitor and adjusting the end bells to correct for the rubbing, I turned it on to find it makes a loud noise (not from rotor rubbing) and heats a lot after running for less than a minute. Can you help me to find out the cause? Thank you very much.

ANSWER: I sounds like the start winding is not coming out of circuit. It also could be a shorted winding. Check the centrifugal switch to make sure it has not moved on the shaft, thus not allowing the switch to open.

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wiring diagram
wiring diagram  
QUESTION: I checked the centrifugal switch and is working fine. Regarding the windings, can you tell me how to check them?  I'm attaching the wiring diagram. I have a very basic analog multimeter, I hope that is enough.

About the only thing you could do with the meter, is to check continuity, and the resistance of the windings. But for that to be accurate, you would need to know the original resistance as it came from the factory. The continuity test will not detect a shorted winding, only a open circuit.

I'm thinking what you are referring as a run capacitor, is actually a start capacitor. There is a way to test the start winding, by by-passing the internal stationary switch and centrifugal switch. You will need insulated pliers to do this. Remove one lead from the capacitor. Now touch the lead back to the terminal and start motor, and then quickly remove lead from the capacitor. This does the same as the internal switching system, as soon as the motor starts, it takes the start winding out of circuit. Now, one of two things will happen. The motor will run normally, or do the same as before, which will indicate a shorted run winding.

Let me know if the motor runs normally, and then we will work on the start winding. If it still runs bad, nothing more can be done, as the run winding is shorted.  

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Charles C. Jones


Let Me help you with your problems with single phase and three phase electric motors. I can tell you how to troubleshoot your motor problems. From simple testing of capacitors, how to test your windings, replacing bearings, and general maintenance. Before we go any further, remember these words of advice: Disconnect the power before you do anything! Please limit your questions to electric motors and there immediate components. I review each question, and if I can answer or help, then I will. If you receive a rejection, it means it is out of my expertise, and just do not have the answer. I'll be waiting for your question.


I have 40 years experience in the repair of electric motors and related equipment. I am a master machinist in the field of motor repair. I was employed with my company for 35 years, but retired in May of 2013. The downside to that is I lost access to a lot of technical data. I will still try to give you the most accurate advice that I can.

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