Given a bench grinder which did not work. How to test/fix?
I cleaned all the wiring connectors etc and used a 4-way extension cord with an i/o switch and thermal/arc breaker surge protector thingy. I had a piece of thick cable with a molded three prong plug which I had removed from a dead paper shredder (I think??) and connected the ground to the case (previously not connected) the black to the black and white to the white. I taped the connections and plugged the test cable into the extension thingy with its switch off and plugged it into the wall outlet. Then, with the grinder switch on, I gingerly switched on the extension thingy and the grinder (sans all moving parts) ie just the motor case and spindle (held securely in the B&D workmate) and viola(!) it worked fine and built up to very fast. I switched off the grinder switch and the motor slowed, taking an age to come to rest.
Then, I fitted a grinding wheel on the left hand thread end, tightened everything and retested, using the grinder switch to start it and it spun really fast.
Soooo, I guess the secure ground is an essential feature of a capacitor induction motor. I checked some old furnace motors that were "maturing" in the basement and they had no capacitor but only 2 wires...
I am now trying to remember which parts came off last and put it all back together. I plan to test it each time I put a part back...just in case. I hate it when you fix something on the bench and when rebuilt, it won't work...don't ask about the electric starter on the snowblower..not a happy puppy!
Please, pretty please and then some, do tell me if my "fix" is wrong and I could risk all kinds of nastiness.
on Jun 13, 2018