Need help with troubleshooting AC ELectric Motor

[Clive]

Gentlemen (and Ladies) -

Helping out a friend. Craftsman 10" radial arm saw. Was told it
worked when put away. Now the motor hums when turned on. Giving it a
little push gets it turning slowly.

The 120V motor has a very slim profile. I found a capacitor external
to the motor. Replacing it made no difference. I also observe that
the wiring from the motor (3 leads, wht, blk, red) as well as the AC
from the on/off switch and the capacitor connect to a square gadget
with spade lugs. The L1 line apparently goes through a heavy wire
coil that bridges two of the terminals, to what I assume is the run
winding lead of the motor. (blk)


This gadget has a marking "3CR 118 931". I would like to know what it
is and also the likelihood of it being the problem. There isn't much
to it, I don't know if it is actually anything more than a terminal
block.

If it will help I can scribble up a wiring diagram or even attach a
photo of the device.

Regards - Tony

 

[Homer J Simpson]

Helping out a friend. Craftsman 10" radial arm saw. Was told it
worked when put away. Now the motor hums when turned on. Giving it a
little push gets it turning slowly.

Possibly a PSC motor with one burned out winding.

--
..
..
..
..
..
..
..
..

 

[James Sweet]

Gentlemen (and Ladies) -

Helping out a friend. Craftsman 10" radial arm saw. Was told it
worked when put away. Now the motor hums when turned on. Giving it a
little push gets it turning slowly.

The 120V motor has a very slim profile. I found a capacitor external
to the motor. Replacing it made no difference. I also observe that
the wiring from the motor (3 leads, wht, blk, red) as well as the AC
from the on/off switch and the capacitor connect to a square gadget
with spade lugs. The L1 line apparently goes through a heavy wire
coil that bridges two of the terminals, to what I assume is the run
winding lead of the motor. (blk)


This gadget has a marking "3CR 118 931". I would like to know what it
is and also the likelihood of it being the problem. There isn't much
to it, I don't know if it is actually anything more than a terminal
block.

If it will help I can scribble up a wiring diagram or even attach a
photo of the device.

Regards - Tony

Have you looked into getting a manual from Craftsman? Most decent power
tools have replacement parts available and the manual will show what
everything is.

 

[Clive]

The "gadget" turned out to be a motor start relay. The start winding
was not getting switched in. Google up "3cr motor start relay" if you
are curious.

Thanks for taking the time to respond.

- Tony