Sears Radial Arm Saw Motor Problems

I hope someone can help me. I was given a Sears Radial Arm Saw that does not work. The model number is 113.197750. When I turn it on, the motor hums but does not turn. I turn the motor when it is on and it turns freely but will not spin on its own.
I have done some searching on Google and tried some of their solutions without success. I took the motor apart and cleaned out all the sawdust. In addition, I banged on the arbor as someone mentioned but it did not fix anything. All the copper wiring on the motor that I can see looks new. There are no dark or burned spots on the copper.
I tried a multimeter on the incoming power and it is getting 120 volts. The strange thing is that the leads to the capacitor do not register any power when the motor is on. I checked it a few times and the best it showed was 1 volt but it quickly went to zero. On one try when I left the motor on for a few seconds, the motor turned 1/4 revolution then stopped. I could not get it to turn anymore on its own. Does that mean it needs a new capacitor? I am not very knowledgable with a multimeter but think I checked it correctly.
I would love to get the saw working as it is in great condition and I learned that a free repair kit is available since the saw has been recalled. Any help anyone can offer would be appreciated.
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There is pretty well no doubt that the starting winding is not being engaged. I have had mine do exactly the same thing several times and MY solution was to blow high pressure air into the housing which I am sure just dislodged some debris from the starting centrifugal switch. After that, it worked like a charm. I don't know what year yours represents, but mine is over 30 years old. I have never changed out the starting capacitor, but from your measurements, I would say your problem is the same. Test the impedance across the centrifugal switch contacts. If they are open, you need to clean them. That may be no more than just wiping debris from between the contacts. If that does not work, take some fine (600 grit) sandpaper and fold it in half with the grit out on each side. Place the paper between the contacts and see-saw the paper between the contacts to clean them. If the impedance is 0 when you measure the impedance, trace the starting winding to see if you can detect a brake.
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Are you sure the motor is wired for 110? Sounds like a symptom of a 220 wired motor being plugged into 110.
Don

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That motor uses a centifical switch and a capacitor to run. Either one could be bad. The capacitor may be the easist to just replace, any motor shop should have one for less than $10. The centrifical switch may be more diffecult as it requires some dissassemly of the motor. Greg
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Thanks for all your help. I will try the compressed air from my compressor tomorrow. I had used a small can of air but I do not think it did a great job. Higher pressure air might do the job.
I am not sure what the centrifical switch looks like. Can anyone describe it or where it is located on the motor? I looked at the part sheet for the motor on Sear's web site but it does not list a part called a cetrifical switch.
BTW, I figure the saw is about 20 years old.
Thanks again.
Glen
Greg O wrote:

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don't list it in the parts diagram. An electric motor repair place would be your best bet to find the correct part.
What the switch does is disconnect the start winding when the motor gets up to about 75% full speed.
If this switch is does not engage, then the motor will not start with external aid (which might be a bit dangerous). If the capacitor is bad, the motor will not start either. Jim
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I tried my compressor to blow air on the motor but it did not help. I think taking the motor apart to find the cetrifical switch is a little over my head. I will try replacing the capacitor first and see if that helps.
I do have another quesiton. I found a part on the saw motor that looks like it should be connected to something that it currently is not. If possible, please see pictures of the motor on the following:
http://www.geocities.com/gtannenb/Motor1.JPG
http://www.geocities.com/gtannenb/Motor2.JPG
http://www.geocities.com/gtannenb/Motor3.JPG
The part in question is in the first picture and it is the two copper leads coming out of the clear plastic casing. It is located on the back end of the motor and appears that it has solder on it. Should it be connected to something and/or could it be causing my problems?
Thanks for all the help.
Glen
Jim wrote:

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It could be the start switch! Is it possible someone tried to fix this motor before you got it? I see a yellow wire nut that looks out of place too. Most factory connections are spade connections, wire nuts are not typical.
Maybe time to take it to a motor shop!
Have you checked to see if this saw falls into the safty recall that Sears has out? You may just want to collect the $100 from the recall and move on! Greg
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OK, now I feel like an idiot. I was looking at the motor again tonight and realized that per the instructions on the main wiring block, it was wired for 240 volts. Once I changed it to 120 volts, the motor started right up. I am not sure if there is any torque on the motor as it was disassebled and I did not feel like putting my hand on it when it was disassembled.
This does raise a few questions that maybe someone can help me with.
1. Since it was set to 240 volts on the wiring block, are there any other changes made to the motor to get it to work with 240 volts?
2. I was surprised to see that it still had a 120 volt plug on the motor. Does this indicate that someone was probably playing with the motor and not really using it for 240 volts? I thought that it would need a new plug to be used in a 240 volt outlet?
3. Does this have anything to do with the possible disconnected part I mentioned in my previous posting?
I will put the saw back together in the next few days and test it out. As I mentioned, I hoped to get it working because it is recalled but I am eligible for an upgrade kit and not the $100.
Thanks for everyone's help.
Glen
Greg O wrote:

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I have an older Sears RA saw that works well. It does not qualify for the upgrade kit, they want the motor and then I get the $100. Beings I like to live dangerously I decided to keep the saw! Greg
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The centrifical switch is in the end of the motor. If I remember correctly, it is in the end oposite the saw blade. There is a set of weights that swing out as the motor comes up to speed which moves a hard plastic ring. The movement of the ring operates a switch contact. The switch contacts should be closed when the motor isn't running, but should open to disconnect the capacitor and start winding when the motor reaches about 1000 RPM.
--
Charley


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