Stairmaster Alternator Brush Replacement Video

Video about How to Replace the Motorola Alternator Brush for Stairmaster Equipment

This video demonstrates how to change the brushes of a Motorola Leece Neville alternator used on Stairmaster fitness equipment.

NOTE: It is not necessary to remove the alternator from the machine to replace the brushes.

Tools needed:

  • 1/4" socket or wrench
  • Commutator Cleaning Stone


  1. The brushes are found under the brown cover that is located around the base of the field terminal on the alternator.
  2. To remove the brushes, begin by first disconnecting the field wire from its terminal.
  3. Then remove the screws from the brown cover using the 1/4" socket or wrench.
    1. Be careful when removing the screws as the brushes are under a spring load.
      1. This will result in some movement upon releasing the screws which will release the stored energy of the springs.
  4. Now remove the cover.
  5. At this point, you can gently push the brush assembly at an angle toward the center of the alternator and lift it out as shown in the video.
    1. Proper use of this method can aid in the removal of the brush assembly without damaging it.
  6. The brushes shown here are unused.
    1. Worn brushes will have a rough surface as well as being shorter than the pair shown.
      1. A brush 1/4" long or shorter is questionable.
  7. Generally, worn brushes will also leave quite a bit of carbon dust in the alternator which can increase resistance between the brushes and the commutator.
    1. Therefore it is always a good idea to use a commutator stone, as shown in the video, to clean up the surface of the commutator before installing a new set of brushes.
      1. Note: Using forced air to blow the carbon dust out of an alternator is not good practice. It can release the powder carbon into the air and inhalation of this can be harmful. Use of a vacuum with small attachments is the only safe option.
    2. First, locate the surface of the commutator by noting the surface the brushes rub against when installed.
    3. Focusing on one side of the surface at a time, spin the alternator pulley a few times while holding slight pressure against the commutator with the cleaning stone.
      1. Doing so will clean and prepare a fresh surface for the new brushes to make contact against.
  8. NOTE: Your brush assembly may come with a small metal or plastic rod inserted to hold the spring loaded brushes in place. If equipped, you will need to remove the small metal or plastic rod that is holding the brushes in the assembly before installation. If it is not removed damage to the electronics may occur.
    1. Rod is installed to reduce the possibility of damage to the spring-loaded brushes during shipping.
  9. To reinstall the brushes you will notice they are spring-loaded, if you start in at an angle and press toward the center of the alternator, once you get it on top of the notches, as seen in the video; place the cover over the brushes while holding tension and then reinstall the screws.
  10. Once the screws have been replaced, reconnect the field wire to its terminal on the alternator.
  11. The procedure for replacing a Motorola alternator brush on Stairmaster equipment is complete.
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