Tip & How-To about Stairmaster Exercise & Fitness

Alternator Testing for 4400CL, 4600CL, and SC916 Steppers

The video demonstrates a unit with no resistance, the pedals fall to the floor. Checking that the alternator brushes are working properly is the recommended action. Tools Needed: 1/4" Nut Driver or Wrench
This is done by disconnecting the brown wire from the Field terminal of the alternator and the white wire from the B+ or POS terminal of the alternator. The wiring sticker should help you to identify the designated terminals. A jumper wire is needed to proceed with this test. (A jumper wire can be fashioned from wire with slip on connectors crimped to each end or the jumper can be a normal piece of wire with the coating stripped from each end. The designated terminals have a small hole that the stripped end of the wire can be threaded through to create the jumper.) Connect one end of the jumper wire to the B+ or POS terminal and the other end to the Field terminal. Step on the unit for about 10-15 seconds to verify resistance. If no resistance between the B+ or POS and Field, this normally indicates that the alternator brushes are worn or damaged.
Remove the jumper wire and then remove the alternator brushes for further inspection. Using the 1/4" driver or wrench, remove the two bolts from the brush cover. Once the bolts are removed, pull on the Field terminal to remove the alternator brushes.
Inspect the alternator brushes. The brushes should be smooth and free of cracks, nicks, and breaks. The brushes are spring loaded. Confirm when pressed that the brush will spring back to position. Replace the brushes if necessary.
When re-installing the alternator brushes to the alternator, the brushes will face down toward the inside of the alternator. (Due to the brushes being spring loaded, it may be necessary to press the brush into its housing for ease of installation and to avoid damaging the new brush.)
Test the unit after replacing the alternator brushes. Reconnect the jumper wire to the B+ or POS terminal and the Field terminal. Step onto the unit and verify resistance. In this example, the alternator brush replacement was all that was necessary to correct the resistance problem.
With resistance verified, it is time to remove the jumper wire and reconnect the white wire to the B+ or POS terminal and the brown wire to the Field terminal. Make sure all cables are connected (including the console cable) and this completes the alternator test

Testing Alternator of Stairmaster Steppers 4400CL 4600CL SC916

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stairmaster pedal resistance electrical problem

How To Clean Commutator Using Commutator Stone
Did you use a commutator stone when installing the new brushes? A commutator stone is used to remove carbon build up from the commutator of a motor or alternator, which is created from worn brushes. The commutator is the internal part of the motor or alternator that spins and makes contact with the motor or alternator brush.
BE ADVISED: The dust created from cleaning the commutator is a carbon dust. Use caution when removing dust so as not to inhale.
If servicing the motor or alternator without removing from the unit, be sure to disconnect power from the machine.
To remove the carbon build up from the commutator, first remove the brush from the motor or alternator. Insert the commutator stone into the brushes place in the motor or alternator. Apply slight pressure against the commutator stone and by hand, slowly turn the motor or alternator shaft. As you are turning the shaft of the motor or alternator, the commutator stone cleans away the carbon that has built up on the commutator.
Use a vacuum hose to suck out the dust debris or tip the motor/alternator over and allow the carbon dust to fall out.

I am also attaching a video on how to install the brushes just for an extra reference.
Stairmaster Alternator Brush Replacement Video

Jan 20, 2014 | Stairmaster Exercise & Fitness

1 Answer

slipping pedals on stairmaster 4400 freeclimber

Start by checking the alternator brushes. Worn brushes are the leading cause of no resistance issues in these machines.


Dec 03, 2013 | Stairmaster 4400 PT Stair Stepper

1 Answer

my stairmaster 7000 pt has no resistance

I would suggest checking the brushes in your alternator. The alternator is the component that provides the resistance in this unit.

Repair Parts for Stairmaster Equipment Batteries Springs Belts Chains...

Nov 29, 2012 | Stairmaster Stepmill 7000 Pt

1 Answer

both pedals slipping to floor as if no power was getting to it. screen reads stepper when first plugged in

I would start with checking your brushes in your alternator. If they are worn down, they will not make good contact. The resistance in this machine is provided by the alternator.

Testing Alternator of Stairmaster Steppers 4400CL 4600CL SC916

Sep 09, 2010 | Stairmaster 4600 Cl Cordless Freeclimber

1 Answer

Both pedals slip?

When both pedals slip at the same time, it is more likely to be the alternator brushes than it is to be the hub assembly. Check this link for a brush replacement video. I am also attaching a troubleshooting video for no resistance on a 4600PT.

Stairmaster Alternator Brush Replacement Video

Sep 08, 2010 | Stairmaster 4600PT Stepper

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