How to Troubleshoot Electrical System on Stairmaster 4000PT

Stairmaster Stepper 4000PT Electrical SystemTroubleshooting


  1. Verify that the AC wall outlet is supplying the correct power in one of two ways:
    1.  Use an AC voltmeter to verify that the AC line voltage is between 100 and 120 VAC (or between 220 and 240 VAC, if applicable) at the AC wall outlet; or
    2.  Plug in an alternate AC-powered device (a lamp, for example).  If the device does not work when plugged into the AC wall outlet, consult an electrician for further assistance and then retest the AC wall outlet
  2. Plug AC cord from the power supply back into an AC wall outlet.
  3. The green LED on the power supply should now be on.  If the light is not on reset the circuit breaker on the power supply by pressing the breaker in.  If the LED still does not light up, replace the power supply.
  4. Disconnect the DC cable from the machine, between the power supply and the side panel, and for 15-17 VDC in pins #1 (positive) and #2 (negative).  Replace the power supply if the voltage reading is outside the specified range.
  5. Remove the side covers.
  6. Reconnect the DC cable to the side panel power connector and locate the black and white wires on the backside of the power connector.
  7. Follow the white power connector wire to the alternator and unplug it from the main cable white wire.
  8. Set your voltmeter to DC voltage. Connect the positive lead of your voltmeter to the white wire from the power connector and touch the grey casing of the alternator with the negative lead of your voltmeter.
  9. DC voltage measured should be 15-17 VDC. Replace the power connector if the voltage is outside the specified range.
  10. Reconnect the two white wires.
  11. Locate pins #1 (positive) and #9 (negative) in the main cable connector that plugs into the console and measures DC voltage.
  12. DC voltage measured should be 15-17 VDC.  Replace the main cable assembly if the voltage is outside the specified range.
  13. If all voltage readings have been within the specified range and the console will not power up, the console should be replaced.
  14. Check for loose wiring connections on the alternator, diode, and load resistor.
  15. Preform the Positive Output to Field test:
    1. Turn the power off.
    2. Remove the black wire from the B+ terminal on the alternator.
    3. Remove the brown wire from the field terminal on the alternator.
    4. Place alligator clips on the B+ terminal and the field terminal of the alternator.
    5. Step on the machine for 15-20 seconds.
    6. If full resistance is achieved during this time, your alternator has the correct current flow.
  16. Remove the brown wire and diode from the field terminal of the alternator and set your voltmeter to the lowest resistance setting.
  17. Place one lead from the voltmeter on each end of the diode, and record the number shown on the voltmeter. Then reverse the leads and record the number shown.
  18. A diode that is in proper working condition will show a high reading in one direction and a low reading when the leads are reversed.
  19. Replace the diode if the readings recorded are both high or both low.
  20. Remove one wire from the load resistor and set your voltmeter to the lowest resistance setting.
  21. Place one lead from the voltmeter on each of the threaded posts on the load resistor. Record the number shown.
  22. A load resistor in proper working condition should read approximately 0.5 ohms.  If the number recorded is outside the specified range replace the load resistor.




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