If defects are detected (breaks, cracks, wear) replace the brushes. The procedure for replacing the brushes is illustrated in the photos, which also show brushes of some recommended types. To install Anco brushes, press the button and move it to remove the worn brush. To remove Trico brushes, find the widened part of the brush and use a screwdriver to press the retainer, inserting the blade between the holder and the metal base (support plates) brushes. Some Trico brushes have two metal crimping clips and the brush should be removed from the holder clamps. The brush is inserted first into the front clamps, then moved back and inserted into the remaining clamps. Regardless of the type of brush, you should always follow the instructions provided.
Make sure that as you push the brush in, all the clips are holding the brush in place. Make sure the brush is installed correctly. Otherwise, the holder or metal base of the brush may scratch the glass.