is my Canadian Tire TS.
The switch started acting up after I had owned it for 6 mos. I would have to flick the switch up/down dozens of times, even hundred to get it to start. Once on, it stayed on until I shut it off again. While quickly repeatedly flicking it, it seemed the power was getting through at any point along the throw of the switch. It was getting a minor spark to the motor with minor partial rotation during many non-contiguous times flicking. I had a premonition which has just now come true. Now when plugged in and running, the OFF position does not stop rotation. I have to unplug the cable to stop rotation. I can plug it in to start it while it is in the OFF position. The switch does have an integral plastic safety "key", which pulls out, but probably isn't any part in the problem. The key used to work properly; now, in or out, it doesn't matter.
My local CT may be the type of place I could likely take the switch, or other faulty component, and get another one, but I wouldn't know what or if I could do anything about it myself; not knowing how the switch would connect to the motor, or the motor to the switch, etc.. I haven't looked. I may need to revisit this post after this initial consultation.
Is it the switch, or could it be the motor or anything else?