Volvo: Volvo 240 - 1991 Model, volvo 240, wind screen

Question
Wiper jumping / rattles

This has been my problem ever since I bought this car.
Have change the motor, wiper arm , blades but problem still exist. Mechanic told it could be the wind screen itself. Ater 2 years chnge the wind screen due to crack. But  even though new windscreen the problem never goes away. Do not know what else need to change. One noticeable point is that as you run your fingers on the wet windsreen it is sticky. Tried all sort of clearner but no luck. At the moment my only solution is to have soapy water in the windcereen washer container. When it rain keep injecting soaping water for smooth wiper. Will last 2 to 3 min with every spray of soapy water. Any Idea?  

Answer
Ravindran Pillai,
I have only seen the wiper arms not positioned correctly on the windshield. I then take a small adjustable wrench and bend the arm where the blade attaches until the blade goes over the window without chattering. The wiper arms and blades need to be perpendicular to the windshield.