Unisaw On/Off Switch Help

[ryan feasel]

I have a 2nd hand 36-825 Unisaw that has worked great for years. Yesterday the saw started for less than a second, then stopped. The blade turns freely. There is power all the way to the switch. It does not appear there is a "reset" button on the motor itself. I'm hoping it's the switch and not the motor. The on/off switch appears to be original. I'm sure this switch, 438-01-016-0194, is no longer available. Any suggestions on how to test the switch with a volt/ohm meter? Thanks in advance.

[Bruce King]

You can usually measure resistance between two large red wires then two large black wires while pushing the switch but yours has some different wire colors.
The best way is to remove the cover plate on the motor where the wires enter and check the voltage while pushing the on switch. Be advised that the motor start capacitor will still have either 120 or 240 still across it. My 240v saw has 120v across the 120v start capacitor.

[Alex Zeller]

What it looks like is when you push the start button the contactor (black thing on the left) will be pulled in by a coil in the bottom of it. One simple test you can do is using a small piece of wood (non conductive) very carefully push in on the 4 tabs on the top of the contactor with the power connected up. Have the blade all the way down as if the motor is good it'll start up. Again, be very careful not to touch anything else inside the box as the wires and terminals will have power on them. When you release the tabs if the saw stays on then the coil is good and the start switch is most likely the problem. If the motor shuts off then the coil is most likely the problem. If the saw doesn't come on then it's most likely a motor problem.

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[ryan feasel]

Well that's not good. I just plugged the saw in and depressed the 4 tabs with a piece of wood. Nothing happened.

[Alex Zeller]

The next step would be to see if there's power at the motor when those tabs are pushed in. I assume you have a multi-meter but a non contact voltage tester works great for this. They are cheap and I've seen them at Harbor Freight and Home Depot. They work well to find blown Christmas lights too. If you place the tip next to the power cord it'll light up if there's power on it. It's possible that one of the contacts inside the contactor is burnt up or it's a motor issue. The other way to test it would be to put the starting box back together and remove the cover to the motor and measure across the two wires with power on them. You should have 240v when you push the start button.

[Matt Day]

Could also bypass the switch and hardwire the motor to test it.

[ryan feasel]

This seems strange, maybe it's not. Using a non-contact tester, I determined there is power to the motor through the switch as soon as I plug the saw in. I don't have the press anything on the switch for the power to flow from the wall, through the switch, and to the motor. I would have expected it to stop at the switch unless I pressed the contacts. ???

[Bruce King]

Your picking up the voltage still on the start capacitor I mentioned earlier.
My saw broke today and it’s fixed, read this thread for info
https://sawmillcreek.org/showthread.php?287665-3-hp-240-volt-motor-not-starting

[Stan Coryell]

This seems strange, maybe it's not. Using a non-contact tester, I determined there is power to the motor through the switch as soon as I plug the saw in. I don't have the press anything on the switch for the power to flow from the wall, through the switch, and to the motor. I would have expected it to stop at the switch unless I pressed the contacts. ???

You need to measure voltage. It looks like L1 and L2 are where power come in. You should measure 240v there. Did you check the breaker?

[Bill Dufour]

While pushing the start button check voltage between t1 and t3. If no voltage push in the resets with a piece of wood and measure again while holding it closed. Does it make any noise at the switch when you push the start button? I am suspicious of the stop button circuit. Blow any dust out of the switches and the contacts. Wiggle each wire then tighten each terminal screw.
Bill D

[ryan feasel]

Well, I was able to get the saw running again. I manually exercised the centrifugal start switch a few times. It seemed to be working properly. I also replaced the stationary start switch with contacts. $30 for peace of mind. Not sure which did the trick, but it runs, that's all I care about.

[Dan Hahr]

Stop switch was probably stuck depressed. Happens to mine occasionally. Sharp bump loosens it just fine.

Dan