Belt sander motor pulsing rpm

E

Ebel440

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Hi im new to the forum and this is my first post besides my introduction. My problem is with a belt sander with a 1/4 hp capacitor start motor. I was given the sander and i was told the motor ran but seemed to run a little slower then it should. I did not test it at that time. I brought it home and tried it out but the motor keeps pulsating on and off. The whole start stop cycle only takes a few seconds but will continue if plugged in. I serched the internet but nothing described this problem. I believe that it may only be running on the start winding and it stops once the centrifugal switch cuts out and then the cycle repeats. My question is has anyone had this problem before and is it repairable or should i look for a new motor? The motor is covered in steel powder and oil and alot inside it. Possibly some was dislodged in my trunk and got in the motor should i start cleaning it out or is it a lost cause? Thanks Ed
 
Ebel440 said:
I believe that it may only be running on the start winding and it stops once the centrifugal switch cuts out and then the cycle repeats. My question is has anyone had this problem before and is it repairable or should i look for a new motor? The motor is covered in steel powder and oil and alot inside it. Possibly some was dislodged in my trunk and got in the motor should i start cleaning it out or is it a lost cause? Thanks Ed
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Don't think you'll know for sure till you take it apart but you can alway check the continuity of the windings with an ohm meter.
 
Sounds like it is just trying to run on the start winding's. Could be that the run winding's are fried, or maybe the centrifugal switch is dirty. The good news is that 1/4 HP motors are pretty cheap.
 
Ebel440 said:
Hi im new to the forum and this is my first post besides my introduction. My problem is with a belt sander with a 1/4 hp capacitor start motor. I was given the sander and i was told the motor ran but seemed to run a little slower then it should. I did not test it at that time. I brought it home and tried it out but the motor keeps pulsating on and off. The whole start stop cycle only takes a few seconds but will continue if plugged in. I serched the internet but nothing described this problem. I believe that it may only be running on the start winding and it stops once the centrifugal switch cuts out and then the cycle repeats. My question is has anyone had this problem before and is it repairable or should i look for a new motor? The motor is covered in steel powder and oil and alot inside it. Possibly some was dislodged in my trunk and got in the motor should i start cleaning it out or is it a lost cause? Thanks Ed
Click to expand...

Your theory sounds quite likely. Take it apart, clean it, and see if you can find a loose connection in the run circuit. Motors are pretty simple machines. It's usually obvious what's wrong.
 
Thanks for the replies i will take it apart and check the run windings and try to give it a good cleaning. I have another motor that should fit if it turns out no good.
 
does it turn freely...if not it is just trying to reach full speed
 
Ebel440 said:
Thanks for the replies i will take it apart and check the run windings and try to give it a good cleaning. I have another motor that should fit if it turns out no good.
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I'll be watching for your diagnosis as I have a band saw that acts like that. I have a replacement motor and will change it out but if I can fix the bad one so much the better.
 
Hi i just opened the motor and checked the resistance of the run winding and i am getting a reading of zero. I have never had to check motors like this before so am not sure what it should read but i believe that i should have some resistance. Am i correct to believe this indicates a short in the winding. Besides that there are some arc burns by the contacts on the switch and the motor is full of sanding dust. I checked the other conections and nothing is shorting to ground.
 
Well i gave the motor a good cleaning not perfect but took out a large pile of dust and reassembled it. It now runs but seems slow which is what i was told when i recieved it. The resistance readings i took may be incorrect due to shorting through the dust or my multimeter could be acting up i dont completly trust it. Im unsure what would cause the motor to run slow it has no load and the bearings appear good. It may also be that the winding is shorted and acting as a shorter coil. Thats the only thing i can think of that would explain it. At this point i will reassemble the sander and see how it works and if it works well enough ill use it as is. Thanks for your help
 
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