1. Check the condition of the brushes. Replace worn brushes. The brushes should also be replaced if they are not cleaning the glass effectively enough. It is recommended to replace the brushes annually.
2. To remove the brush, move the brush holder lever away from the glass until the lever is locked. Turn the brushes 90°, press the inner brush lock with a screwdriver or finger and remove the brush from the lever hook, pulling the lever out through the groove in the brush frame.