How to Troubleshoot No Resistance on Stairmaster 4000PT


No resistance on a Stairmaster 4000PT stepper can be caused by either a mechanical failure or an electrical failure. This flowchart and notes are to help you troubleshoot the electrical causes for no resistance on your 4000PT.

WARNING! Before performing the alternator test, make sure to unplug the unit from its electrical outlet.



  • Jumper Wire with alligator clips on each end
  • Multimeter

Flow Chart Notes

  • NOTE 1:
    • Change Console to Rev. E
      • While in the ATTRACT mode, press 9750 followed by ENTER and retest for a resistance problem.
  • NOTE 2:
    • Place a jumper between pins 2 and 4 of the gray cable
      • Remove power from the unit and unplug the gray cable from the console.
        • Short pin 2 to pin 4 (a paper clip works well).
        • Reapply power and begin stepping.
          • You should have full resistance.
  • NOTE 3:
    • Perform Alternator Circuit Tests
      • Alternator Test #1
        • While in the ATTRACT mode, press 107, followed by ENTER and 1.
          • Press down on either pedal and the lower-left LED should come on.
            • If it does not, you should check the connection of the blue wire to the alternator.
      • Alternator test #2
        • While in ATTRACT mode, press 107, followed by ENTER and 2.
          • Press down on either pedal and then press the SPEED UP arrow.
            • The lower-left LED should come on and you should have full resistance.
              • If not, check the connection of the brown wire to the alternator.
        • Press start to clear/cancel either test.
  • NOTE 4:
    • Test the Diode on Alternator (if equipped)
      • Disconnect the ground (NEG) side of the diode ONLY and retest.
        • If the resistance is normal, the diode is defective.
        • The diode could also be tested with a multimeter. You would have a low resistance reading in one direction and a high reading in the other.
          • A high or a low reading in both directions would mean a defective diode.
  • NOTE 5:
    • Place Jumper on Alternator
      • Remove power from the unit.
      • Remove all connections from the alternator's output and from the field.
      • Using a short lead with alligator clips, connect the output to the field and begin stepping.
        • You should gain full resistance in about 15 seconds.
  • NOTE 6:
    • Test the Load Resistor
      • Disconnect either lead of the load resistor from the alternator.
        • It is a .5 ohm resistor and should measure 1 ohm or less on your multimeter.
  • NOTE 7:
    • Test Continuity of the Gray Cable
      • The gray cable pin 2 should have continuity to the brown wire and pin 3 to the blue.
      • The black and white wires (pins 5 and 4) are good if you have power to the console.
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