i have a 91 420sel where when i close the roof from the open or tilt position it doesnt stop in the closed position, just keeps going to the next open position(tilt or ful open) i'm told if you pull out the white plug on the motor unit and turn the roof manually you can "time' the transmission so the roof will stop in the full closed postion. does anyone have any idea how this works? im trying it but i dont seem to get the right combination.