Stairmaster 4000PT Stepper Alternator Belt Replacement Procedure

This procedure covers the steps required to replace the alternator belt on a Stairmaster 4000PT.

Tools Required:

  • 19mm Wrench
  • 13mm Wrench
  • Or an adjustable wrench


Note: We begin with the shrouds removed and the power disconnected from the machine. It is important to note that you are only required to remove the user's left shroud to access the alternator belt. Both shrouds were removed in this video for clarity only. 


  1. Loosen the nut that holds the alternator to the frame

  2. Loosen the bolt that holds the alternator to the adjustment bracket

  3. Pivot the alternator down to create enough slack in the belt to slip the belt off the pulleys


Note: Proper belt tension leaves 1/4" (0.6cm) of deflection in the belt with fingertip pressure at the midpoint between the two pulleys.

  1. Slip the new belt onto both pulleys

  2. Pivot the alternator back upward to create tension on the belt

  3. Tighten the nut and bolt previously loosened

  4. Inspect your machine to ensure that all hardware is tight and components are properly assembled before installing the shrouds

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