I have a 98 silhouette I belive to be the best model..... the problem is that I was driving down the road and even when the windshiled wipers were on the off position they would randomly come on and run for a bit then go down and set them selves then come up like they are going to wipe then go down and set a couple of times and its really annoying. is this some kind of switch behind the arm, is it really expensive is it really hard to change? any help would be very appreciated.