If it's the remote switch..they get full of dust and start going squirrely on ya. I got a replacement under waranty on my PM switch and after a few months it went bad too. Then i discovered a post by John Lucas on another forum telling how to clean the switch. Haven't had a problem since. To prevent a recurrence, I put the remote inside a zip lock bag to keep the dust out. You can operate it with the bag on just fine. Here's John's post:
"My Powermatic 3520 remote switch died this weekend. It had acted up several time in the past. I don't hardly ever use it so I was a little hacked. Fortunately it was an easy repair. Woodcraft also sells a remote switch that appears to be very similar to this so maybe this will save someone some time.
Take the box apart and take the switch out. You'll have to push the little plastic latches on the ends of the switch toward the switch and at the same time push the switch out. That's by far the hardest part of the repair.
The switch is held together buy two plastic spring latches located on the sides of the switch. Pry these out and seperate the switch housing. There is a rubber dust cover. Pull this out. clean it off. It apparently doesn't work all that well because my switch was pretty dirty.
There are two plastic pins that push on the rocker arms. Don't lose these they are just floating in some holes. Pull the metal rocker arms out and clean them off. It only takes a very small amount of dust to keep this style of switch from working.
put them back in, correct side up. Now put the rubber dust cover back in. Then put the top part of the switch back on and snap the plastic springs over their clips. Put the switch back in its box and put the box back together. Not a difficult repair at all. "