4400 PT suddenly goes faster than level 20 after 1 minute

Replacement Parts for Fitness Exercise Equipment at SPORTSMITH

This really sounds like a resistance issue. This can be caused by worn alternator brushes or a bad alternator. The alternator provides the machines resistance. The following information is for checking the brushes and further troubleshooting information.

Replacement Parts for Fitness Exercise Equipment at SPORTSMITH

This could be caused by worn alternator brushes. The following link will take you to a video on testing the alternator. If the alternator checks out, you may be dealing with a faulty display console.

Video about Performing Jumper Test on Stairmaster Alternator

Transmission is slipping, Take it in to a transmission shop.

1.Check the device's battery level for at least two bars of strength.
2.If the battery level is low, charge the battery.
3.If the issue is not resolved, remove the back cover.
4.Remove the battery.
5.Wait 10 seconds.
6.Press and hold the W key.
7.While pressing down the W key, re-insert the battery.
•The device restarts and after approximately 15 seconds, the 'Recovery' screen appears
•Release the power button but *continue holding the home button*, for another 30 seconds.
Step
Thanks

More than likely, your power supply is not providing the correct amount of voltage. You are looking for 14-19 volts DC. Power Supply Kit with Plastic Output Connector Domestic Stairmaster...

Display reads CONFIG RQRD or NTM CONFIG RQD on Stairmaster Equipment Probable Cause The message CONFIG RQRD or NTM CONFIG RQD appears when the console needs to be configured for the machine type it is installed. This message is common when the console has been replaced or if the settings have been changed. Message is commonly seen on various Stairmaster equipment such as bike models 3000CE, 3300CE, 3400CE, 3600RC, 3800RC and 3900RC; stepper models 4400PT, 4600PT, 4400CL, 4600CL and SC916; stepmill models 7000PT and SM916; elliptical model ClubStride 5100.
Corrective Action

• Make sure the unit is in an "idle" state. "Idle" state means the console is not displaying an error or any message that requires data input. The display should basically be freshly powered up, scrolling the EKG or welcome message
• Configure the console for the proper machine type by pressing Level UP, 80, ENTER
• Using the Level UP or Level DOWN keys, scroll through to the proper machine type (Bike, Elliptical, Stairclimber or Stepmill)
• Once the proper machine type is shown on the display select the machine type by pressing ENTER
• This completes the steps necessary when your Stairmaster display reads CONFIG RQRD or NTM CONFIG RQD

Stairmaster Console Message CONFIG RQRD or NTM CONFIG RQD

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Remove console knobs form the back of the console, lift the up, and disconnect the 20 pin cable from the console. Get a multi meter go to dc volts 100v range. On the connector you will be testing for 12 to 19 volts. When Looking at the connector the connector nipple should be pointing left starting form the bottom left odds numbers right bottom even you will hunt for pin 1 Neg pin 10 Pos. If all voltage readings are within 12 to 19 volts and the console is not powering up , then either replace or have the console repaired.
National Gym Parts can help with process go to http://www.gympart.com/

Replace the drive hub. You can try greasing it with a good lithium grease but probably to late.

Replacement Parts for Fitness Exercise Equipment at SPORTSMITH

This sounds like an issue with the console. It is almost like a software glitch in the programming. Before focusing on the console as the culprit, you can check the wiring leading up to the console for good continuity just to make sure the wiring isn't the issue. I will attach a link to a video on using a multimeter to assist in checking the wiring.

Video about Multimeter Testing