1999 BMW 840Ci mileage: 87,000. I have a question regarding my driver side power window system. About two months ago, the window started acting up. The symptoms are: 1. Whenever I tried to close the window, it always stopped in the middle. I have to try to press the power window button several times in order to fully close my window. What caused this problem? Is it the switch going bad, the control module or the motor? 2. There are also times when I could not even open or close the window. I have to wait several minutes in order to do anything with that window. 3. Where should I start to diagnose the problem?