Dust Collector Motor Troubleshooting

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Blog entry by CodyC posted 05-17-2012 12:52 AM 11607 reads 0 times favorited 7 comments Add to Favorites Watch

Hi Lumberjocks,

I need some help diagnosing an issue I’m having with my dust collector. Recently my dust collector started tripping the circuit breaker and running with a lot of vibration. Initially I thought it was the impeller that was out of balance, but now I’ve at least narrowed it down to the motor (after wasting $80 on a new impeller).

This first video shows the motor running completely assembled…and then the noises that follow as it shuts down…

...and here is the motor running after I removed the impeller and the detached the housing from the motor. Hopefully the audio comes through enough for you to tell what is going on…

I have no experience with fixing motors. Do any of you small motor experts want to lend some advice? Do I need to replace the bearings? If so, then any tips on how to get started?

-- Cody Crisp

7 comments so far

View dbhost's profile


5767 posts in 3378 days

#1 posted 05-17-2012 02:31 AM

Not sure about that specific make / model how it’s built or anything like that but generally speaking a high pitches whine like that is a bearing going bad. Replacement can be simple, or complex depending on the motor. I haven’t done much electrical motor work, and it has been a VERY long time, if you have a shop that works on motors near you, it might be worth your hassle just to take the motor in and get it rebuilt. Cost shouldn’t be too bad depending…

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View cabmaker's profile


1740 posts in 2954 days

#2 posted 05-17-2012 02:36 AM

Sounds like they got some rice in it at the factory.

View CodyC's profile


39 posts in 3575 days

#3 posted 05-17-2012 03:53 AM

Quick update – the dust collector is a Shop Fox W1685. The motor is 1.5 HP, 16 Amp 110V single phase, runs at 3450 RPM.

-- Cody Crisp

View MacSteveT's profile


55 posts in 2839 days

#4 posted 05-17-2012 04:23 AM

I can’t tell from the video – is this a capacitor start motor? Cap start motors use an AC capacitor at start up to get the motor started spinning. Most cap start motors have a centrifugal switch that is closed when the motor is not spinning, but opens up as the motor spins up to operating speed. This switch removes the capacitor from the circuit once motor is spinning, because it is no longer needed, and could burn out if it stayed in the circuit with the motor running. The centrifugal switch is usually mounted on the tail shaft of the motor, and is spring loaded with small weights – as the switch spins, the centrifugal force against the weights cause the springs to compress, which opens the switch. Here is a pic of what a typical switch looks like.

From the first video, the “click” sound you hear at approx 13 seconds is the centrifugal switch popping into the open position as the motor slows down after the power is turned off. The friction sound that is heard from 14 seconds on to the end sounds like the switch armature is not returning to fully open position, and is rubbing against the switch plate. Dust, small wood chips, and other debris could cause this, or the spring(s) might be failing – you can try blowing the motor out with compressed air, to see if it makes a difference.

It is hard to tell if there is bearing squeal, or if it is the switch rubbing. Given the sounds from the spin down, I would guess its the switch. Now, in the second video I can’t tell if the motor is spinning up or not, but the loud hum sounds like a problem with the start capacitor – either it is not engaging at all, or is engaged all the time – either one of these scenarios point to the centrifugal switch.

In the end, you might well be able to disassemble the motor and diagnose the problem yourself, or, you can follow @dbhost’s advice and take the motor to a shop that rebuilds AC motors. Diagnostic fees are usually $30 – $40, but I really don’t know what a full rebuild would cost. Most shops would require a full rebuild instead of a repair or part replacement because they don’t want warranty issues down the road.

Harbor Freight sells electric motors for reasonable $ if the rebuild is too expensive – it might be worth looking there just to see. Hope this helps,

Steve T.

-- "Do, or do not. There is no try." ~Yoda

View FreshSawDust's profile


68 posts in 2475 days

#5 posted 05-17-2012 02:58 PM

My 2hp Grizzly was doing a similar thing so I took the cover off the motor and found that there is a fan blade on the shaft that set screw had worked loose and it was the fan hitting the cover. The fix was a dab of threadlocker and tighten the set screw with an allen wrench.

-- TJ - Perryville, Missouri

View CodyC's profile


39 posts in 3575 days

#6 posted 05-18-2012 06:28 PM

Quick update…I disassembled the motor last night and at least found that the fan was not hitting the cover. After I got into the guts of the motor I realized there was not too much more that I could do at my level of expertise. I called and got a price for a new motor from Shop Fox…$150 + tax and shipping, so probably $200 when all is said and done.

I called a local electric motor service shop and they said they generally don’t charge just to diagnose the issue, so I’m taking the motor in for them to look at on Monday.

-- Cody Crisp

View exelectrician's profile


2328 posts in 2573 days

#7 posted 06-06-2012 04:22 AM

Hi, CodyC,
The centrifugal switch is stuck in the on position probably from repeated starts in quick succesion. These switches can only be repeatedly started once every 60 seconds or so (which is considered normal operation). To repair this problem take the motor apart starting at the fan end. Remove the fan cover screws or bolts holding the end of the motor and remove the end cover. You will see a whole lot of wires coming from the terminal box, motor windings etc,. The centrifugal actuator is a pair of small weights that operate a spring loaded toggle that engages in the switch. Ensure this actuator clicks in and out smoothly, look at the contacts, they are probably welded on each other. Gently pry them apart. Using a nail file, VERY gently smooth off any jagged bits of silver contact, try and leave as much of the remaining silver as possible even if it is blackened, this is quite okay, and will prolong the life of the contacts. Carefully reassemble the motor ensuring the centrifugal switch assy will work without interference from other wires etc,. – You just saved $$
The purpose of the switch is to switch off the starting windings once the motor gets up to about half speed. From the sound of the video I can hear the centrifugal switch clicking in and out but the loud hum is the starting winding, not switching off, I have heard this sound many times.

-- Love thy neighbour as thyself

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