In this article we will show how it is possible to understand when a treadmill motor is faulty and how to repair it.

Most common causes for damaging a treadmill motor
Damages to treadmill motors happen usually because of excessive load. The load on the motor depends on the user weight, the user speed, the way of walking/running on the treadmill and the friction factor which develops between the mechanical parts of the treadmill.

User behavior
We can’t reduce the user weight, and we can have a little effect on the personal way of walking on the treadmill. Other factors may be considered to improve motor life.
Starting the treadmill with your feet on the running belt is always a bad thing. The motor will request a very high current demand from the controller, this may result in damage to the motor windings, damage to the controller and quite often for 90/130v motors in the de-magnetization of the motor.

The de-magnetization of the motor happens because the permanent magnets used in home-use DC motors are magnetized in the factories using a strong electromagnetic field. An opposite electro-magnetic field could de-magnetize the magnets.
When a motor is de-magnetized, it tends to absorb high current even with low load (you will feel a reduced torque) and goes too much fast compared to a standard motor.
Another common mistake is to use 16km/h treadmills to walk at less than 3 km/h. Due to the design of the treadmill motors, the DC motors commonly used in home-use treadmills have a good efficiency and heat dissipation at high speed. Using the treadmill at low speed for a long time overheats the motor windings and may damage the motor windings and / or the motor controller. Every time it is possible please try to keep your minimum speed at least 1/3 of the max speed of the treadmill (for a 16km/h treadmill it should be 5 km/h)

Maintenance
Lack of maintenance is another issue that affects many treadmill owners. Most of the running decks need to be lubed regularly, and the motor compartment should be hoovered to avoid too much dust and dirt from forming inside.
Even with good maintenance after several years it may be necessary to replace the running belt with a new one. The reason is that over time the plastic of the belt becomes less flexible and increases the friction factor. Even a small increase of this friction factor between the surface of the deck and the lower texture (white) of the belt will cause a strong increase in the motor current consumption and may bring problems to the motor and the controller.
Make sure the motor is your problem
If the motor is mechanically blocked, noisy, if sparks come out of it when running, or small black pieces of plastic come out of it, it is pretty sure that you have a problem with your treadmill motor.
While if your treadmill doesn’t start at all, or if you are experiencing low torque, it may be that your problem is not the motor.
Fix the treadmill motor: mechanically blocked, noisy, sparks, pieces come out of the motor

Mechanically blocked
If the motor is totally blocked (i.e. you can’t turn it freely with your hands), most of the time you need to replace totally your motor. It may be that with some force it could be possible to turn the motor again, but this is very risky. When the motor gets blocked, it is because the internal winding protection overheated so much, that it welded inside the motor. Cooling out, this material becomes hard and may block the motor. Every time the winding protection has melted, there is a very high risk of short circuits inside the motor windings which should be totally insulated from each other. Those short circuits will make your motor collapse in a short time and frequently will damage your treadmill controller if you keep using it.

Noisy treadmill motor
Regarding noisy motors, we have two kinds of situations. The easier one is if the noise comes from bearings. Motors have bearings on their axe. Sometimes they become noisy, especially if the motor pulley is misaligned or the drive belt is overtight. Replacing the bearings is totally safe and any good mechanic should be able to replace them.
The worst situation is when the noise comes from the motor collector. That may seem a similar noise to the one of broken bearings but it is totally a different cause. The collector of the motor is made of thin copper lists, which transmit the current from the motor brushes to the motor windings. Sometimes due to bad use big sparks generate, so big that they can damage the lists, so that the space between themselves is not regular.
When this happens there is a chance to rectify the motor collector, but usually also the windings have been damaged so our suggestion is to replace the motor.

Sparks  
When sparks come out of the motor it may be a collector problem (see above), but if you are lucky, it may be caused by worn brushes. Worn brushes may be simply cleaned with sandpaper or replaced with new brushes of the same type. If the treadmill is used properly brushes won’t get worn easily because the charcoal used for treadmill brushes is pretty hard and they are expected to last for the treadmill lifespan. If you need to replace the brushes because they are worn, be careful to do proper maintenance and keep the right behavior to avoid the problem to happen again shortly.

Pieces of plastic come out of the motor
This is a bad situation, if plastic comes out of the motor, then the winding insulation is gone. That is not plastic, in fact, rather special insulation resin.

Smell / Smoke comes out of the motor
This may look very scary, but it is one of the situations which may be fixed if you haven’t melted the motor insulation. When the motor is overheated the internal part may reach 100-150°C so the insulation resin of the windings begins to melt and any dust and dirt begin to cook.

Repair your motor: worn brushes, interrupted winding on the collector, dirt and dust in the motor, broken plastic parts.

Worn brushes
Replacing the brushes is easy: just turn off the treadmill, wait a couple of hours to allow it to cool down, then open the brushes caps. Standard treadmill motors have two plastic brush caps, which are usually snap-fit or may be screwed.
Remove the caps, extract the brushes, check their size, buy a replacement (a small tolerance in the size is allowed), install the new ones. Job done!
If the new brushes get worn in a short time, or the motor still performs badly, you need to replace the motor.

Dirt and dust in the motor
Dirt and dust may form inside the motor, especially if you don’t hoover the motor compartment regularly. Hoovering is simple, but please be careful! If the motor has small plastic/resin pieces inside, that’s not regular dirt! It means that the winding insulation inside your motor has melted. You must replace the motor and be more careful with the maintenance and with the lubrication of the running deck.
Interrupted winding on the collector
Developing an interrupted winding on the collector is rare, and it happens usually when the motor has lost its insulation. Anyway, sometimes it may be that a single winding is interrupted on the collector by mechanical stress (or poor manufacturing).
In this case welding the winding again will fix the problem. This is something a specialist should do! Avoid DIY in this, because you may risk creating a short circuit and more damage to the motor and to your treadmill controller.

Broken plastic parts
Treadmill motors usually have a plastic fan, which may get broken. That is easy to replace, it is usually fixed in its place by a Seeger ring, or just snap-fit.
Other plastic parts may be broken accidentally such as the motor brushes caps. You may break even the motor brushes compartment, which is made in plastic for some manufacturers (as instance on most of Proform/Weslo/Nordick Track motors).

Consumption of a good motor
A DC treadmill motor in good standing should absorb no more than 1.5-1.8 A when connected to the treadmill belt with no load (nobody on the treadmill).
A motor tested on the bench (with no drive belt connected) should absorb about half (.4 to max .9A).
The motor current consumption should be stable and shouldn’t have any peak (except for the initial peak at start-up) when the motor is tested on the bench or on the treadmill without load.

A motor tested on the treadmill with the load of a regular person shouldn’t absorb more than 6-7A. The maintenance and the friction factor of the running belt may change dramatically the current absorption.
If your motor differs from the above values, it may have developed a winding fault or de-magnetization fault and you should replace it or seek specialistic technical advice for special maintenance on your treadmill. By keep going with it as it is, you will damage the motor controller and incur in more costs to fix your treadmill.