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normspanners
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My thoughts exactly the only other thing I thought about is, do they do that grinder in 110v maybe the wrong cap has been fitted previously (or from new even) and because it is 240v thats what they stuck in ? I think it is the centrifugal switch welded together.
You would have been better to have ordered a cheap clamp on ammeter to test it rather than a voltmeter, connecting a clamp meter to the cap would test the centrifugal switch (if there is one fitted) and the capacitor. does it state on the rating plate which cap should be there.
normspanners
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Generally yes BUT that is not guaranteed, As EIL says run it with the clamp on on the switch wire to the cap and see if it is A/ drawing power on run up and B/ switching out at high revs.
Assuming you have a centrifugal switch on the motor (since you think you can hear a click of it closing when slowing down) clamp around one of the wires on the capacitor and start it up. It should show a quick spike in current then drop to zero once the centrifugal switch opens. You can also spin it up as you do now and take the current draw while its running see if it matches what is on the rating plate if it has one.
I'm wondering if old Ming Fun calls a starting capacitor by the same name we do though, as normally a start cap would be in a range like the one you tried to replace it with, and a run cap would have a definite figure like 80uf.
Norm quicker on the draw there
I'm wondering if old Ming Fun calls a starting capacitor by the same name we do though, as normally a start cap would be in a range like the one you tried to replace it with, and a run cap would have a definite figure like 80uf.
Norm quicker on the draw there
We don't know what his system is yet though do we, If it is cap start induction run and the switch is not opening then it will blow the start cap as well as draw more current when running, you have only highlighted half of my quote there. If the spike in current doesn't drop off when up to 3/4 of its speed then the centrifugal switch is stuck on. Does that sound better 
But it doesn't run, what part of that don't you understand? you will only see the spike of the cap charging and the current falling off in a working system, if the cap was charging and the motor was starting he wouldn't have started the thread?? A simple continuity check across the two wires to the cap with a meter set to ohms and the motor stationary will say if the switch it closed ready for starting, I would of thought as the motor won't start it is most likely the switch is o/c otherwise the motor would start but then destroy the cap if the switch didn't disconnect.
What I understand is that he put on a new capacitor and it worked for a while then blew the new cap, he has the put another cap on and that's gone as well, that's 3 caps blown, that suggests to me that the capacitor is left in circuit, rather than not be in circuit due to a o/c centrifugal switch as you suggest.
A simple continuity test across the centrifugal switch with the motor stationary would indeed show if it was o/c or not quite right. but a clamp on meter on the cap to switch wire would also show whether it was in circuit on start up and whether its disconnecting when up to speed. The OP did say it was ok for a while when he changed caps.
Perhaps we could get more photos of the wiring when he gets back on line but it sounds that he will have to do a bit of exploratory surgery.
A simple continuity test across the centrifugal switch with the motor stationary would indeed show if it was o/c or not quite right. but a clamp on meter on the cap to switch wire would also show whether it was in circuit on start up and whether its disconnecting when up to speed. The OP did say it was ok for a while when he changed caps.
Perhaps we could get more photos of the wiring when he gets back on line but it sounds that he will have to do a bit of exploratory surgery.
Cracked it !!!
Thanks to all your help, i tested the resistance across the capacitor wires and had none , so I stripped it down and found 10 years of crud around the centrifugal switch contacts, a quick scrape and a bit of contact cleaner and Hey Presto, with both new capacitors. I checked the original Cap and it is indeed US.
Once again thanks for all your help, I will go and buy the polishing mop for it now.
Thanks to all your help, i tested the resistance across the capacitor wires and had none , so I stripped it down and found 10 years of crud around the centrifugal switch contacts, a quick scrape and a bit of contact cleaner and Hey Presto, with both new capacitors. I checked the original Cap and it is indeed US.
Once again thanks for all your help, I will go and buy the polishing mop for it now.
