Should you determine that the contacts are clean and your switch is functioning, then it is likely that the motor has burned out and is in need of replacing. Installing a BMW window regulator
or a regulator for any other make the steps involved in replacing a window regulator are usually quite similar:
1. Remove the door panel for the affected window.
2. Locate and remove the bolts holding the regulator to the door; it is likely you will have to manually lower the window in order to access the bolts.
3. Remove the old regulator, disconnect all wiring, and replace the old regulator with a new one you have purchased from a parts supplier. Shop online to find the best value as you will pay a mint if you order one through a dealership.
4. Tighten the bolts holding the new regulator and reinstall the moisture barrier. Make sure all the wires are put back in the door before closing the door panel.
5. Engage the power window switch and the new regulator should work unimpeded.
Of course, follow your carís repair manual for specific instructions.