I have a Craftsman radial saw 113.29440. The motor hums when the switch is engaged. I,m thinking I have a problem with the start relay. I have already replaced the capacitor. To further my investigati
First, please check if the blade is free to rotate by hand when the saw is unplugged. If it isn't then either there is some debris caught under the blade guard or the bearings are froze up or the push button that locks the arbor so you can turn the blade removal nut with force is engaged with the arbor and is stuck there.
Second, make sure the motor is not wired for 220v and you are trying to run it on 110v. (See the plate on the side of the motor. Lots of motors can run on either, but require hooking up the wires differently under the cover where the wire enters the motor. There is typically a wiring diagram under said cover.)
Third, You say you have a "start relay". That would be a box mounted on the saw base below the table with push buttons to start and stop the motor. The box contains a magnetic contactor that closes when you push the start button. It is held in place by an electro magnet until the "OFF" button is pressed or power is lost for some other reason. This is a safety feature so that if the power goes out and then comes back on later, the saw wont start up on its own without pressing the start button. These contactors typically contain a thermal fault protection or a 'heater' that also shuts the motor off when the amperage gets too high.
Fourth, In case you meant "starter winding" instead of "starter relay", that would be inside the motor and there is a centrifugal switch that switches from the starter winding to the run winding when the RPMs are sufficient. Sometimes those switches get stuck. Read More At : Saws...