[porsche tech]

The rubber on the blade must fold side to side depending on which way it is moving across the windshield. If it does not, it will result in chattering and all kinds of other noises. The easiest way to detect if they are folding properly is to turn off the key in the middle of the swipe and see if the rubber edge of the blade is folded to the correct side. Porsche actually had a special tool to adjust wiper are angle back in the day. It was a plastic cylinder with a slot that could be slipped over the arm to bend it so that the blade would sit squarely on the windshield and thus fold side to side depending on direction of travel. The same thing can be accomplished with a pair of duck billed pliers and a rag (to prevent scratching the arm). Even new blades will make noise if not adjusted properly. Hope this isn't TMI.--Dave