windsheild wipers wont shut off

I have a 2000 Lesabre and all of a sudden the wipers wont shut off. When i first turn them on they will work for a couple of times but then they stick on. I have puled the wiper motor out and looked at it but dont see anything wrong. It is all printed curcit board. Has any one else hade any problems like this. My dealership is not much help.