Originally Posted by
bergerud
I wonder if it was from opening the cover to interrupt the machine. It seems to me that this is how the switch gets damaged. It is not protected from the back emf surge from the motor. Sparks jump in the switch when the motor current is interrupted.
I don't think that this is the case. A properly-designed switch should be able to actually switch current and not just allow it to pass with no damage. Switches are rated for the number of contact closures at current:"The contact rating is the voltage/current that the switch can repeatedly connect and interrupt without degrading it's design life-cycle operation count."
I think dust more likely. My "close cover" switch failed within a couple of weeks, as did the warranty replacement. I substituted a proper sealed switch and have had no issues since - is it 6 or 7 years now?.