Grizzly GO691 Motor Issues

[Kyle Kaldor]

Today after ripping through 6 sheets of 3/4" plywood for cabinets, my Grizzly GO691 table saw motor is having some issues. I started it up to make my last cut, and it turned very slow and made some weird noises. I would describe the noise as a slight grinding, bogged down noise. I would say the motor was running at about 1/10th the speed it normally does. It was almost like there was some extra resistance on the motor not allowing it to spin up. I haven't had put much time into trying to diagnose the issue, but I did check that the blade rotates freely and blew out the motor on the fan side. There were no bad smells to indicate that something burned up inside the motor. The table saw was purchased new in about 2010. Any suggestions on what to check for?

Thanks in advance,

Kyle

[Chris Hachet]

Put an amp probe on it and see what kind of load it is pulling. Also, check the bearings by removing the belt and spinning the motor with your hands. Third, check for proper voltage at the outlet and at the motor. That ought to be a good start.

[Chris Hachet]

Also, look for something obvious causing a mechanical bind.

[CPeter James]

That sounds like the start circuit is not opening up and the motor is not allows to come up to full speed. the is a sort of governor inside that energizes the starting winding and capacitor. If the governor sticks closed, the motor is unable to ramp up to full speed. These get clogged with dust and dirt or sometimes just bind up because they are too tight on the shaft.
If the start circuit/capacitor were not working of the capacitor were bad, the motor would just hum and not get turning.
CPeter

[Kyle Kaldor]

Thanks for the responses guys. I'm going to go and check a couple of the things you have suggested. Unfortunately, I don't have any way of checking the amperage. Hopefully I'll be able to figure something out soon.

Kyle

[Kyle Kaldor]

Update - after cleaning out my dust collector, which was so full that I got about another 1/3 of a bag full of dust sucked up from what fell out of the plump full bag and dropped out of the canister, I was able to clean out the table saw base and get at the motor. I took off the belts and turned the motor which would spin freely and easily, no binding at all. Checked the voltage at the outlet - 240 V. Took off the fan cover and capacitor covers and blew them out. Both of the capacitor covers were very full of dust. After all of that I replaced everything and fired it up. Still had the same issue. I tested the voltage on the wires after the mag switch and while I was testing it the breaker blew. Obviously that tells me that I'm overdrawing the circuit, but I still don't know why.

Kyle

[scott spencer]

Have you tested the capacitors? It's not uncommon for a modern cap to go bad.

[Chris Hachet]

Thanks for the responses guys. I'm going to go and check a couple of the things you have suggested. Unfortunately, I don't have any way of checking the amperage. Hopefully I'll be able to figure something out soon.

Kyle

An inexpensive Amp probe will come in really handy in tuning tools. I find it a good way to know if something is running right. i like to Amp motors after I change belts or make other adjustments.

[Chris Hachet]

Have you tested the capacitors? It's not uncommon for a modern cap to go bad.Bingo...give the man a cigar. FWIW I try to keep my tools really clean, which is difficult in a wood shop I know. This is not so much a lecture as it is a reality of life for me in Ohio, where we have humidity that rusts anything given a chance.

[Mike Henderson]

Normally, a bad cap will keep a motor from starting, it will not cause it to run slowly. And I'm afraid that CPeter is incorrect. There is no governor in the motor. Once a single phase motor starts to rotate it will generally come up to full speed, whether the starting circuit is disconnected or not.

If the problem is that the motor starts up properly but does not come up to full speed, and has a grinding noise, I'd suspect that the bearings are bad and the rotor is rubbing on the stator. Sometimes the pressure of the belts pulling to one side - if the bearings are bad - will pull the rotor into the stator.

Mike

[Chris Hachet]

Normally, a bad cap will keep a motor from starting, it will not cause it to run slowly. And I'm afraid that CPeter is incorrect. There is no governor in the motor. Once a single phase motor starts to rotate it will generally come up to full speed, whether the starting circuit is disconnected or not.

If the problem is that the motor starts up properly but does not come up to full speed, and has a grinding noise, I'd suspect that the bearings are bad and the rotor is rubbing on the stator. Sometimes the pressure of the belts pulling to one side - if the bearings are bad - will pull the rotor into the stator.

Mike


Makes sense. Bearings were one thing I suggested, which is why I wanted the OP to pull the belt and try spinning the motor by hand. Normally when bearings start to go i can feel it when I turn a motor by hand...

[CPeter James]

I have to differ. I had a Grizzly motor on my milling machine that did just that. the starting circuit was sticking closed and kept the motor from spinning at full speed. I rebuild motors and machines as a source of income and this is not an uncommon problem. If the motor has two capacitors, one will be the start and one will be the run. It is possible that the run capacitor is bad. but I still think my original diagnosis is worth checking out. BTW, there is a governor in most larger single phase motors to control the starting circuit.
CPeter

[Chris Hachet]

I have to differ. I had a Grizzly motor on my milling machine that did just that. the starting circuit was sticking closed and kept the motor from spinning at full speed. I rebuild motors and machines as a source of income and this is not an uncommon problem. If the motor has two capacitors, one will be the start and one will be the run. It is possible that the run capacitor is bad. but I still think my original diagnosis is worth checking out. BTW, there is a governor in most larger single phase motors to control the starting circuit.
CPeterI also have a capacitor tester among my shop tools. Paid sixty dollars for it several years ago and it has come in very handy...

[Kyle Kaldor]

Thanks again for the help. Can someone walk me through how to check a capacitor and what I'm supposed to be looking for. Is this done when the motor is powered up or off? By the way I'm fairly certain it's not the bearings. The motor would spin freely with no play or grittiness, very smooth.

Kyle

[Chris Hachet]

Test it with a capacitor gestor or just buy new capacitors for the unit. Capacitors probably less than ten dollars apiece at an electrical supply house.

Also, double check all of the electrical connection points inside the saw. Table saws create lots of vibration and that creates havoc with connections.

[Kyle Kaldor]

After some testing with a multimeter, I believe it is the run capacitor that is bad. I've decided to replace both capacitors, but Grizzly wants $45 for the run capacitor and $30 for the start capacitor. Searching to find a replacement seems to be a daunting task with endless possibilities. Does anybody have a go to place for capacitors?

Kyle

[Dan Friedrichs]

Kyle, what leads you to think the run capacitor is bad? (You may be right - just curious what tests you did).

I usually buy motor capacitors from McMaster.

[CPeter James]

You can buy capacitors on Ebay or your local motor repair shop. They should be in the $10 range on Ebay.
CPeter

[Chris Hachet]

After some testing with a multimeter, I believe it is the run capacitor that is bad. I've decided to replace both capacitors, but Grizzly wants $45 for the run capacitor and $30 for the start capacitor. Searching to find a replacement seems to be a daunting task with endless possibilities. Does anybody have a go to place for capacitors?

Kyle
Most major cities ahve motor repair shops that do repair work for the trades...I would start there.

[Kyle Kaldor]

Kyle, what leads you to think the run capacitor is bad? (You may be right - just curious what tests you did).

I usually buy motor capacitors from McMaster.

Dan, I set my analog multimeter to 1k ohms and tested. The start capacitor jumped to near 0 ohms and went back to infinity. The run capacitor did move the needle somewhat indicating some resistance initially, and then back to infinity, but nearly as much resistance as the start capacitor. I'm going to check at work today for a capacitor tester. If we have one I'll hold off on ordering the capacitors.

Kyle

[Kyle Kaldor]

Chris, unfortunately I don't live in or near a major city. Not sure if I have any motor repair shops close.

Kyle

[Chris Hachet]

Granger has something like 600 listings for motor capacitors, you might start there.

[Dan Friedrichs]

Dan, I set my analog multimeter to 1k ohms and tested. The start capacitor jumped to near 0 ohms and went back to infinity. The run capacitor did move the needle somewhat indicating some resistance initially, and then back to infinity, but nearly as much resistance as the start capacitor. I'm going to check at work today for a capacitor tester. If we have one I'll hold off on ordering the capacitors.

One thing you might try (just for curiosity sake) is to repeat the test you just described, then repeat it again with the multimeter leads flipped. If there is some initial charge on the capacitor, you might not see the "dip to zero", but if you flip the meter polarity, you will.

In any case, it's hard to definitively test a capacitor. I'd just buy a new one for ~$10 from McMaster and see if it fixes the problem.

[Chris Hachet]

One thing you might try (just for curiosity sake) is to repeat the test you just described, then repeat it again with the multimeter leads flipped. If there is some initial charge on the capacitor, you might not see the "dip to zero", but if you flip the meter polarity, you will.

In any case, it's hard to definitively test a capacitor. I'd just buy a new one for ~$10 from McMaster and see if it fixes the problem.


If nothing else this gives you a spare on hand. I have replaced lots of capacitors on motors through the years.

[Kyle Kaldor]

One thing you might try (just for curiosity sake) is to repeat the test you just described, then repeat it again with the multimeter leads flipped. If there is some initial charge on the capacitor, you might not see the "dip to zero", but if you flip the meter polarity, you will.

In any case, it's hard to definitively test a capacitor. I'd just buy a new one for ~$10 from McMaster and see if it fixes the problem.

Dan, I tested it with the polarity flipped several times and would get the same results either way. I found out that we have a capacitor tester at work so I'll be taking that home tonight to test them out. I'll look for replacements in the mean time.

Kyle

[Chris Hachet]

Dan, I tested it with the polarity flipped several times and would get the same results either way. I found out that we have a capacitor tester at work so I'll be taking that home tonight to test them out. I'll look for replacements in the mean time.

Kyle Good luck, I hope it works out for you!

[Rod Sheridan]

Dan, I set my analog multimeter to 1k ohms and tested. The start capacitor jumped to near 0 ohms and went back to infinity. The run capacitor did move the needle somewhat indicating some resistance initially, and then back to infinity, but nearly as much resistance as the start capacitor. I'm going to check at work today for a capacitor tester. If we have one I'll hold off on ordering the capacitors.

Kyle

Kyle, that's because the run capacitor is only 10 to 20% of the capacitance of the start capacitor.

It sounds like you have an open start circuit which could be a loose wire, failed or stuck centrifugal switch or open start winding (least likely).

Regards, Rod.

[Kyle Kaldor]

Kyle, that's because the run capacitor is only 10 to 20% of the capacitance of the start capacitor.

It sounds like you have an open start circuit which could be a loose wire, failed or stuck centrifugal switch or open start winding (least likely).

Regards, Rod.

Rod, where is the centrifugal switch located? I'm not seeing that on the diagram. Would that be located in the Mag Switch Assembly?

Kyle

[Dan Friedrichs]

The centrifugal switch is mounted somewhere on the motor shaft, maybe near the motor's cooling fan. Do a google image search for "centrifugal switch" and you'll see that it's really just a few pieces of spring steel.

Given that your motor starts running, though, I think the run capacitor is more likely than something with the starting circuit.

[Ken Fitzgerald]

Centrifugal switches generally look like the points in an old automobile engine and function in a similar manner. The one I saw was located at the non-pulley end of the motor. Simply removing the motor end cap, I was able to blow it out.

[Kyle Kaldor]

So I was able to check the capacitance of the capacitors. The 25mf capacitor read 23.3mf and the 200mf capacitor read 236mf. Looks like I'll be searching for a different solution. I'll have to check the centrifugal switches as others have suggested. I'll check some other connections as well.

Kyle

[Kyle Kaldor]

Update - I took the entire motor off the table saw, took it apart and cleaned and blew it all out. There was some dust in the motor, but not a lot. I also inspected the centrifugal switch and found the contacts looking black and crusty. I hit them with some emory cloth to clean them up. Put everything back together and BOOM, it works!!!

Thanks to all who helped me out and gave suggestions!

Kyle

[Van Huskey]

Good deal.

For people reading this thread in the future doing their own trouble shooting:

1. Grizzly has a video re the centrifugal switch and how to troubleshoot/replace it... yep I am too lazy to look up the addie but it is on youtube

2. if you are looking for motor capacitors locally take yours to the local HVAC supply house even relatively small towns will have them and they usually will have what you need, the counter workers are usually quite helpful UNLESS it is a busy time when the regular customers are piled into the place, try mid-morning or mid-afternoon.

[Ken Fitzgerald]

Good deal.

For people reading this thread in the future doing their own trouble shooting:

1. Grizzly has a video re the centrifugal switch and how to troubleshoot/replace it...

2. if you are looking for motor capacitors locally take yours to the local HVAC supply house even relatively small towns will have them and they usually will have what you need, the counter workers are usually quite helpful UNLESS it is a busy time when the regular customers are piled into the place, try mid-morning or mid-afternoon.

Here you go: http://www.grizzly.com/videos/#?filters=centrifugal%20switch

[Van Huskey]

Here you go: http://www.grizzly.com/videos/#?filters=centrifugal%20switch


Thanks Ken, you are far less lazy than I am...

[Pete Janke]

Update - I took the entire motor off the table saw, took it apart and cleaned and blew it all out. There was some dust in the motor, but not a lot. I also inspected the centrifugal switch and found the contacts looking black and crusty. I hit them with some emory cloth to clean them up. Put everything back together and BOOM, it works!!!

Great news! I also have a 2010 G0691 I purchased new and have been watching this thread. Mine is still going strong.

[CPeter James]

Normally, a bad cap will keep a motor from starting, it will not cause it to run slowly. And I'm afraid that CPeter is incorrect. There is no governor in the motor. Once a single phase motor starts to rotate it will generally come up to full speed, whether the starting circuit is disconnected or not.
Mike

Actually, CPeter was dead on! I work on motors and machines to buy, sell, and repair and have seen this problem many times. I had a Grizzly motor on a milling machine that the starting circuit would not open up until it got to over 1600 rpm on a 1725 rpm motor. What happened is exactly what we had here, the motor stayed locked in the start mode.
CPeter

[Dan Friedrichs]

Is there a difference in behavior when a centrifugal switch fails in a "cap start" vs a "cap start / cap run" motor?

For instance, my impression is that Mike is correct for a "cap start" motor - if the centrifugal switch fails to open, the start cap and auxiliary winding stay energized, and since the start cap isn't rated for such a continuous current, it then usually overheats and fails. But the motor does come up to full speed, doesn't it?

But in a "cap start / cap run" motor, the centrifugal switch needs to switch from using the start capacitor to the higher-impedance run capacitor. If it leaves the start capacitor connected, the slip can go higher, resulting in slower speed? Like how ceiling fans change speed by changing the value of the run capacitor?

[CPeter James]

As long as the cap start circuit is energized, the motor will not come up to full speed. Yes, the cap will probably overhead and go "bang". Motors with run caps will run without the run cap in place or open, but I don't think they will run with that cap shorted. I have seen cap run motors doing pretty good with the run cap not there, just two wires hanging out of the motor. Without the start cap, they just hum and with the start cap circuit locked in and not opening they will get up to a certain speed and make a lot of noise and not go into normal running state. There is a method to determine the correct size of the run cap by measuring the different amp readings in the field coils and balancing them. As for the start cap, its size is less critical with certain limits.
CPeter