Electric bike motor problems: what's going on and what can you do yourself?
At its core, an electric bike is a conventional bike equipped with three essential electrical components: a motor, a battery, and a controller. Although modern motors, such as those from Bosch, Bafang, Yamaha, or Shimano, are very reliable, problems can still arise. In this article, we review the most common electric bike motor problems and explain how to diagnose or fix them yourself.
Written by: Hanna Stevens | January 14, 2025 | Reading time: 4 minutes
More about the author: Hanna Stevens
Hanna is an avid cyclist who loves exploring new routes and sharing her experiences to inspire others to get on their bikes more often.
Key findings
- Always check the brake sensors and cables first.
- Keep the sensors and battery contacts clean.
- Know when it's best to stop and call in a professional
Why isn't the motor running even though the screen is on?
One of the most common problems is a bike that turns on correctly but does not provide any assistance as soon as you start pedaling.
The brake circuit breaker
This is often the first thing to check. The brake cut-off switch is a safety device that immediately cuts off power to the motor as soon as you apply the brakes. If this sensor is faulty or incorrectly adjusted, the motor "thinks" that you are braking continuously and therefore does not provide any assistance.
The solution: locate the brake sensor connector near the levers and disconnect it. If the engine starts working again, the problem is with the sensor. Sometimes, simply adjusting (tightening or loosening) the sensor adjustment screw is enough to restore correct measurement. If this does not work, the brake lever or sensor will probably need to be replaced.
Clogged pedal sensors (PAS)
Electric bikes use rotation (cadence) or torque sensors to determine the level of assistance required. On older models equipped with magnets at the bottom bracket, dirt, oil, or even metal particles can interfere with operation.
The solution: check the sensors near the crank and clean the magnets.
The engine shuts off randomly
Nothing is more frustrating than an engine that suddenly stops, especially on bumpy roads. This often indicates a loose connection somewhere in the system.
Battery connections
Check the battery contacts. If the pins are not tight enough or if dirt has accumulated, vibrations may interrupt the power supply. You can gently clean the contact points with a cotton swab.
Wiring
Vibrations can also loosen connectors located under the screen or near the steering column. If the cables run outside the frame, you can check and reattach them yourself. In the case of internal wiring, it is recommended that you consult a specialist to avoid further damage.
Defective battery holder
Sometimes the battery is not properly secured in its holder. A temporary solution may be to fill the space with foam, but for a lasting solution, the holder will need to be repaired in a workshop.
Error messages and communication issues
Modern electric bikes are complex systems in which the motor must communicate with the battery and the display. According to studies, the most common causes of motor failure are:
- Problems with the drive unit
- Poor communication between the engine and the display
- Defective sensors
- Outdated or faulty software
The speed sensor
A common problem observed in practice is the loss of the speed sensor magnet located on the rear wheel. Without this signal, the motor does not know how fast you are traveling and cuts off assistance.
Screen and contact issues
Moisture and cold can cause the screen contacts to oxidize, interrupting the electrical flow.
The solution: remove the screen (if possible) and clean the contacts with a dry cloth. Never use a damp cloth or cleaning products, as this could damage the sensitive electronics. Resetting the screen can sometimes remove software blockages in the motor.
Mechanical problems and unusual noises
Not all engine problems are electronic in nature. A loss of power or strange noises can also have a mechanical cause.
Wheel resistance
Sometimes, brake discs can rub or internal engine components can jam. A simple test is to lift the bike and spin the wheel to check that it turns freely.
Transmission wear
Even though it does not directly affect the motor, a worn chain or cassette greatly influences the efficiency of the assistance. Due to the high power of the motor (sometimes an additional 250 to 600 watts), e-bike chains wear out much faster than on a conventional bike. Replacing the chain in good time (often between 1,500 and 2,500 km) prevents damage to the motor components.
Engine failures related to the battery
The motor can only function properly if the battery is in good condition. If your battery suddenly stops working and no longer recharges, it may simply be a blown fuse. Many batteries have a fuse located at the top or bottom that can be replaced.
In addition, proper battery maintenance is essential to avoid engine problems.
- Keep contacts clean and dry
- Avoid completely discharging the battery
- Recharge the battery preferably at room temperature.
- Do not expose the battery to direct sunlight or extreme heat for long periods of time.
When should you consult a professional?
Although many simple tasks, such as cleaning sensors or tightening cables, can be performed by the user, certain situations require the intervention of an expert. Sources indicate that technical faults in the motor or battery are often the main cause of significant damage.
Certain specific motors, such as the Shimano Steps 6100 and the Brose Drive S Mag, have been found in studies to be more prone to technical faults than those from Bosch or Yamaha. In the event of internal sensor problems, faults on the battery's electronic board, or if the motor needs to be opened for repair, it is advisable to contact a specialist workshop.
Conclusion
Maintaining an electric bike motor requires more attention to electronic connections and sensors than a traditional bike. By regularly cleaning the contacts, checking the speed sensor magnet, and ensuring that the battery is properly charged and securely in place, you can prevent most problems. If the motor still refuses to work, always start with the simplest checks: brake circuit breakers and cable connections. With a little preventive maintenance and a good understanding of these common problems, you'll be able to ride many more miles with peace of mind.
FAQ
Why does my electric bike sometimes work and sometimes not?
Most often due to a loose connection, a faulty battery contact, or a sensor problem.
Can I continue driving with an engine that is running irregularly?
It is possible, but it increases the risk of more significant damage.
How often should I have my electric bike checked?
At least once a year, or more often in case of intensive use.
Is rain bad for the motor of my electric bike?
Not rain itself, but moisture at contact points, yes.
Why is my chain wearing out so quickly?
Due to the additional engine power, the transmission is subjected to higher stresses.