Grinder starter problems

[Hacker]

I have bought caps at Acklands Granger, they have good prices on them. Here is a link to the one that you need on their website it sells for $6
https://www.grainger.ca/en/product/START-CAPACITOR,21-25-MFD,220-250-V/p/WWG12N969

 

[DPittman]

And if you don't have a CS then then there is some electronic equivalent. It could be integrated into the switch or relay or some such black thingy (my electrical knowledge rapidly diminishing here).
I had a video saved but cant find it. This one possibly? John, where are you? LOL

All the info and links so far has been very helpful, thanks for sharing your knowledge folks.

From what I can surmise, my capacitor seems to test ok. My grinder definitely acts as if it has the centrifugal switch mechanism but the schematic and part list makes no mention of it. I'm reluctantly going to disassemble and see what I can either fix or ruin. Here is the schematic for my grinder.

 

[DPittman]

Well it doesn't appear to have any sort of centrifugal switch inside... nothing in end caps but bearings a fan blade and nothing but a rotor and windings for the rest of it. No electronic boxes or gizmos I can see. Just an ordinary on off switch and a capacitor.

 

[CalgaryPT]

"CAPACITOR RUN AC INDUCTION MOTOR- has a capacitor permanently connected in series with the start winding. There is no centrifugal switch so the start winding becomes an auxiliary winding once the motor reaches running speed making it essentially a two phase motor. It does not have the starting boost of a Capacitor Start Motor but does have low starting current which makes it ideal for applications with high on/off cycle rates and fixed loads. They’re considered to be the most reliable of the single-phase motors because there is no centrifugal starting switch. They’re ideal for applications where noise is a factor because they also run very quietly. These motors can be found on fans, blowers with low starting torque and intermittent cycling times, gate operators and garage door openers."

 

[CalgaryPT]

"CAPACITOR RUN AC INDUCTION MOTOR- has a capacitor permanently connected in series with the start winding. There is no centrifugal switch so the start winding becomes an auxiliary winding once the motor reaches running speed making it essentially a two phase motor. It does not have the starting boost of a Capacitor Start Motor but does have low starting current which makes it ideal for applications with high on/off cycle rates and fixed loads. They’re considered to be the most reliable of the single-phase motors because there is no centrifugal starting switch. They’re ideal for applications where noise is a factor because they also run very quietly. These motors can be found on fans, blowers with low starting torque and intermittent cycling times, gate operators and garage door openers."

IOW - the cap could be still be your problem. It's a cheap shot to try even though it tested OK.

 

[DPittman]

IOW - the cap could be still be your problem. It's a cheap shot to try even though it tested OK.

Yup I just reread that too. I think I will head to the city tomorrow and see if I can find replacement capacitor. I'm going to replace the bearings while I have it apart also. One of them is questionble. Should be good for another 20-25 years. Hmmn I should maybe be showing my 9 year old son how to do this so he can do it next time.

Thanks again for all the help and direction. I feel good about it all.

 

[CalgaryPT]

Should have added that the standard cap tests as shown in the video I posted do not register leakage, which occurs more as the voltage increases. The standard tests using a VOM only use marginal voltage from the battery inside the VOM (either digital or analog) and thus are only a one window view of cap health. You need full voltage to accurately test. So your cap still could be bad.

 

[PeterT]

Do you see any wires or black box thingy straddling the shaft or motor that correlates to an rpm pickup type device? This is where my knowledge runs thin but I assumed there must be some kind of feedback that says disengage cap 'now'. And 'now' usually means some target rpm. But I have also heard of timer based systems that assume (when its functioning correctly) motor will ramp up to to rpm after X seconds when switch/relay on. I recall reading something to this effect on another machine when people were flicking the switch on/off quickly & interrupting the logic but I might be completely out to lunch. If the switch looks like a regular on/off & no other sensing features then I think that just leaves the cap. I've read where people have some unobtanium form factor capacitor like old or discontinued machine, so they wire it in externally. Hope it doesn't come to that for you.

 

[DPittman]

Do you see any wires or black box thingy straddling the shaft or motor that correlates to an rpm pickup type device? This is where my knowledge runs thin but I assumed there must be some kind of feedback that says disengage cap 'now'. And 'now' usually means some target rpm. But I have also heard of timer based systems that assume (when its functioning correctly) motor will ramp up to to rpm after X seconds when switch/relay on. I recall reading something to this effect on another machine when people were flicking the switch on/off quickly & interrupting the logic but I might be completely out to lunch. If the switch looks like a regular on/off & no other sensing features then I think that just leaves the cap. I've read where people have some unobtanium form factor capacitor like old or discontinued machine, so they wire it in externally. Hope it doesn't come to that for you.

Oh man now you have me scared. Nope there is no other wiring or black box. What seems to be a speed related click must be a timed function in the capacitor? It definitely clicks when it gets near top speed and if you start grinding/loading before it hits speed it kills everything and you have to restart.