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Motor cutting off just as it comes up to speed

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Forum topic by JJohnston posted 04-23-2010 07:39 PM 1116 views 0 times favorited 11 replies Add to Favorites Watch
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JJohnston

1614 posts in 2756 days


04-23-2010 07:39 PM

The motor on my Grizzly 1276 sander (1725 RPM) shuts off just about the time it gets up to speed, about half a second after I turn it on. If I turn it off and back on quickly, while it’s still spinning, it runs normally. Grizzly says it’s a damaged on/off switch; I’m skeptical of this because it happens every time, not intermittently, and it started happening suddenly, every time, plus (primarily) the fact that it runs normally if I turn it off/on. Anyone know what could cause this? I don’t understand electric motors, except that some of them have both start and run circuits/windings. Could it be these?

-- "A man may conduct himself well in both adversity and good fortune, but if you want to test his character, give him power." - Abraham Lincoln


11 replies so far

View Rick  Dennington's profile

Rick Dennington

5179 posts in 2659 days


#1 posted 04-23-2010 07:59 PM

Greetings JJ….. Sounds like you may have some dust build-up in the switch that’s interferring with the contacts in the switch. That would be my first guess by your description of what’s going on. The fact that the moter runs tells me the moter and windings are good. It’s just not making contact somewhere, and could be a bad switch. Have Grizzly ( I hate them…lol) to send you another switch, swap it out and see. If that’s not it, you have a spare switch….......also could be the brushes… hard to tell without getting into the sander…..

-- At my age, an "all--nighter" is not having to get up and pee...!!!

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JJohnston

1614 posts in 2756 days


#2 posted 04-23-2010 08:10 PM

Well, I’d believe dust buildup, with as much as this thing produces, but again, why wouldn’t it just not run at all? What’s happening in the switch that it starts spinning, then clicks off, then runs again when I turn it off/on? And Grizzly offered to sell me a new switch. How thoughtful of them.

-- "A man may conduct himself well in both adversity and good fortune, but if you want to test his character, give him power." - Abraham Lincoln

View Michael Murphy's profile

Michael Murphy

452 posts in 2470 days


#3 posted 04-23-2010 08:16 PM

When you first start it and bring it up to speed there is a capacitor circuit engaged to help it get up to running rpm. Sounds as if that part is working but the run circuit isn’t closed. Are there vents in the back of the motor? Blow those out with compressed air, thats usually where the centrifugal switches are that turn those capacitor start circuits on or off. In a machine like that, more than likely it’s a totally enclosed motor so someone would have to open it up to clean/repair it.

-- Michael Murphy, Woodland, CA.

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Rick Dennington

5179 posts in 2659 days


#4 posted 04-23-2010 08:22 PM

JJ…. Like I said, it’s hard to know exactly what’s going on without getting into the switch. I’d do that first, and then go from there. It’s not hard to get the switch off.. a couple of screws should be all. I’d take it out, blow it off real good with air, then try again….. this is one of those “scratch your head and think” things. May be just enough dust in there to still let it make contact….. trial and error. Like I said…. I hate Grizzly..won’t even give you a replacement switch if that’s what it is.. By the way…. how old is the sander?
My RAS does that every now and then….gets dust build-up on the points. I have to take it all apart, blow out the dust, put it back together, and it runs great again…...

-- At my age, an "all--nighter" is not having to get up and pee...!!!

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JJohnston

1614 posts in 2756 days


#5 posted 04-23-2010 08:27 PM

The switch will come off easily with 2 screws, but beyond that, I’ll just have to take a closer look, and shoot some air wherever I can.

-- "A man may conduct himself well in both adversity and good fortune, but if you want to test his character, give him power." - Abraham Lincoln

View wchips's profile

wchips

314 posts in 2553 days


#6 posted 04-23-2010 08:33 PM

Like JJ. and Rick say it is probebley the contact switch that connects to the run winding. I have hade the same problem .sometimes if you blow the dust out it will work fine then sometimes you have to take it to a repairman and have them take it down and clean it out. Is the machine still under warenty? if so bug Grizzley until they agree to fix it ir replace the motor

-- wchips

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JJohnston

1614 posts in 2756 days


#7 posted 04-23-2010 09:04 PM

Out of warranty. 2+ years old.

-- "A man may conduct himself well in both adversity and good fortune, but if you want to test his character, give him power." - Abraham Lincoln

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TopamaxSurvivor

17671 posts in 3140 days


#8 posted 04-24-2010 03:19 AM

Sounds like a starting switch to me. The current is so high in the starting circuit, it trips off.

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View lilredweldingrod's profile

lilredweldingrod

2495 posts in 2571 days


#9 posted 04-24-2010 03:25 AM

Hey JJ,
In a lot of electric motors there is switch inside that is called the on/off switch. I think this is where you have the dust and pitch build up. Have tried to blow out the inside of the motor? I have found that you need to regularly give the vent ports a good blow out. If you don’t then you have to follow what wchips said. Rand

View EEngineer's profile

EEngineer

1061 posts in 3078 days


#10 posted 04-25-2010 01:47 PM

This does sound like a stuck centrifugal switch in the motor. If blowing the dust out of the motor doesn’t help, there is a thread on OWWM from someone who recently suffered this problem with links to many past posts that detail how to access the switch and fix it: Here

-- "Find out what you cannot do and then go do it!"

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JJohnston

1614 posts in 2756 days


#11 posted 04-25-2010 04:32 PM

Crap. That looks complicated.

-- "A man may conduct himself well in both adversity and good fortune, but if you want to test his character, give him power." - Abraham Lincoln

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