Chuck, I have a Delta router/shaper with the switch mounted inside, and it also filled with dust. The switch on my DeWalt scroll saw was also of this same design and it too had the dust collection problem. I dis-assembled the switch and removed the dust, and when I re-assembled it I added some electrical tape around the switch body to seal all of the openings. That was about 5 years ago and I haven't had a problem with either switch since adding the tape.
Your switch is likely constructed similar to mine. My switch has some plastic spring clips that hold the switch body together. Prying these out just enough to get the back of the switch body to separate from the front half allows you to get inside and clear out the sawdust. The contacts are similar to a little see-saw in design and the switch lever just pushes them to one side or the other past center. Just be careful not to loose these and put them back in the way that they need to be. Once back together, just wrap a thin layer of electrical tape around the switch body to seal up all of the openings. It should make a huge difference.
Charley
