1.Brush and commutator poor contact or brush wear too short; the grinding brush contact surface, replaced with new brushes.

    2. Brush on uneven spring pressure: Proper adjustment of the spring pressure, so that each brush pressure maintained at 1.47 × 104 to 2.45 × 104Pa, also rely on the hand feeling.

    3. Brush holder will loose brush holder bolts fastening the brush holder and parallel to the surface of the commutator; brush holder from the commutator surface distance is too large; adjust the brush holder to the commutator distance, usually 2 to 3 mm.

    4. Brush grades do not meet the requirements: replace the original grade.

    5. Brush and brush holder mismatch: can not be too tight or too loose, when hot, brush in the brush holder can slide freely, too tight can be used sandpaper to brush appropriate sand to too loose to exchange a new electric brush.

    6. Mica between the commutator segments not pull the net: the hand pull Daoke to remaining mica.

    7. Wrong position of the center of the brush holder: Move brush mountings, select the best location of the spark.

    8. Long-term motor overload: Adjust the load at rated load.

    9. Commutation pole coil short: re-wound coil.

    10. Armature winding open circuit: Open the motor, check the armature winding to identify circuit at the millivoltmeter, if we can not welding rewind.