Another Steel City bandsaw electrical problem - reset button on motor keeps tripping

[Johanna Johanson]

Three months ago I replaced the switch on my Steel City bandsaw. It has (and is) working just fine. Today, however, I have a new problem with that bandsaw - I start it up and in just a few seconds it dies. The reset button on the motor has been tripped. I can reset it and it simply does the same thing again.

Anyone have an idea why? Nothing has been changed - it's on the same 220 circuit that it has been on for years.

[daryl moses]

Sounds like something is in a bind. Have you tried removing the blade to see if the motor will run?

[Ken Combs]

most likely problems:
Start switch isn't opening and leaving the start windings engaged.

the overheat sensing switch that you're resetting is weak.

both are fairly common and easy fix.

[Keith Pleas]

Not specific to bandsaw, but a poor electrical connection on something with high current can cause this effect. Try brightening any screw terminal connections with emery paper.

[Curt Harms]

most likely problems:
Start switch isn't opening and leaving the start windings engaged.

the overheat sensing switch that you're resetting is weak.

both are fairly common and easy fix.


These seem likely. You might also remove the drive belt and try starting the motor with no load. If you have a clamp-on ammeter you could try starting and see how high the start amperage reads.

[Charles Lent]

Your problem is very likely the centrifugal starting switch inside the motor. If it sticks, the motor start windings will stay energized, and the excessive current draw will over heat the motor and trip the overload switch.

Remove the belt from the motor pulley and try running the motor. If the motor still trips the overload after you remove the belt, are the motor bearings free to turn? If you can spin the motor shaft by hand with the power off and without the belt installed? This is a good test for this.

My next step would be to unplug the motor from the power source, remove the motor from the saw and then remove the back cover of the motor, being careful not to loose any shims that need to be between the motor bearing and the bearing socket in the cover. There are 2 or 4 long bolts that run from end cover to end cover that hold the two end covers of the motor on. They must be removed. Then you must pull, pry and tap around the edge of the rear end cover of the motor to remove it. As it's coming off, be careful not to loose any thin metal shims that might be between the end cover and the end shaft bearing of the motor. They must be replaced between the bearing and it's socket in the end cover when the motor is re-assembled.

Inspect the motor windings and vacuum out any sawdust. The windings should be brown or green in color and not black. There should not be any smoke smell in the motor either. If there is, it's time to buy a new motor. Once you let the magic smoke out and the wires are burned in electrical equipment, especially motors, there is usually no alternative but replacement.

If the motor is clean inside and the windings are dark brown or green in color, then you will find the centrifugal starting switch inside the motor back cover. It's just a couple of contacts, one stationary, and one on a springy piece of springy copper. The switch contacts need to be clean and not stuck together, but still touching each other with some spring force. If they are stuck together, this is your problem. Separate them and clean the surfaces so they are smooth with a piece of emery cloth, a very small file, etc. but don't bend the springy piece enough to alter it's shape.

On the moving shaft part of the motor there is a set of spring loaded weights that fly outward from the shaft to move a plastic collar on the shaft. When the motor is assembled, this collar actuates the centrifugal switch as the motor comes up to speed. The area where this collar slides on the motor shaft needs to be clean so the collar can slide easily. If needed, clean this area with emery cloth as well. Then apply a very thin layer of grease to this area of the motor shaft, but keep the amount to just a very thin layer. A synthetic grease or something like Lubriplate would be good here, but just enough to coat the shaft surface.

Re-assemble the motor, replacing any bearing shims that may have come out, being careful not to pinch any wires or get them positioned where they will catch on the moving parts of the motor. Rotate the cover slightly back and forth to find where the long bolts will go all the way through the motor, get all of these bolts to go all the way through the motor before applying the nuts and tightening them. There is a small lip around the edge of the end cover that must fit into the motor as you do this. When all bolts are in place, apply the nuts and tighten them equally, making certain that the lip around the cover edge goes into the main part of the motor all the way around. This is necessary for mechanical alignment of the motor parts.

Spin the motor by hand as fast as you can and listen for the click of the centrifugal switch as you do this. The motor should be easy to spin by hand and you should hear the switch clicking. It is now ready for power again. Test it with power to see if it runs several times before replacing it in the saw.

Try turning the saw by hand turning the pulley to assure that it's also free to turn before installing the belt to the motor. Assure that the motor pulley and the saw pulley are again in line with each other before sliding the motor position to tighten the belt. With the belt tight and the motor mounting bolts tight, the saw should run fine again.

I hope this helps.

Charley