Did you come across that situation in which you were riding your electric bike and suddenly the speed reading disappeared from the e-bike screen and you found error 21 or did a message appear on the e-bike screen that the speedometer does not exist.
If you have been riding an electric bike for a long time, you have most likely encountered this situation.
The reason for this error is that the control motor does not receive a signal from the speed sensor correctly, and therefore the bike cannot work properly.
In this post, we will share together how to test the speed sensor, as well as how to fix problems with it.
How do you test an ebike speed sensor? (Solved)
As a general rule, the speed sensor is tested by testing the position of the magnet in front of the speed sensor and also making sure that the sensor sends the electrical signal to the controller, provided that the sensor is tested using the multimeter
Now let’s move on to the detailed steps to test the speed sensor on the electric bike. As we mentioned, we will do a test for both the magnet and the sensor
Testing Ebike sensor Magnet.
Magnet testing in two ways, the first is to make sure that the magnet is well fixed on the Spoke and that it does not move.
The second method is to make sure that the magnet is completely opposite to the speed sensor, noting that the magnet should be opposite the sensor and not to the screw that holds the sensor in the bike frame.
If you have done the previous two tests and the bike still does not work, you may have to make sure that the sensor itself is working efficiently by doing the following steps.
Testing Ebike Speed.
In order to make a test for the speed sensor, we will need a multimeter and a magnet, as well as 2 conductors of the electric current (you can use a needle)
The idea of the test is to make sure that the switch inside the sensor closes the circuit when the magnet passes in front of it.
- Disconnect the speed sensor cable connected to the controller.
- Set the multimeter to the continuity setting.
- Put a needle in each slot of the sensor plug.
- Put the positive probe of the millimeter on one of the needles.
- Put the negative prop on the second needle.
- Pass the magnet in front of the sensor
If you hear a beeping sound, this indicates that the sensor is working efficiently, but if you do not hear anything, this indicates that the sensor has an internal problem and should be changed.
How to Solve Speed sensor Error 21?
To solve the problem of error 21, which indicates that there is a problem in the speed sensor you should make sure that the magnet is aligned properly with the speed sensor also you need to make sure the speed sensor is close enough to the magnet.
we will start with the problem of the magnet, which is usually the problem of the alignment or Magnet movement on the spoke.
Magnet Alignment Issues.
What is meant by aligning the magnet with the speed sensor is to make sure of two things.
The first is to make sure that the magnet is completely opposite the speed sensor, which can be confirmed by loosening the magnet a little and then moving it so that it is opposite the speed sensor.
The second thing is to make sure that the distance between the speed sensor and the magnet is close enough.
To be sure of this step, you must disassemble the magnet completely and then move with your hand to be very close to the speed sensor and look at the speed reading on the electric bike screen.
If you find the speed reading is moving and the error 21 is gone this means that you should choose a close spoke to the speed sensor and attaches a magnet to it.
If you did the previous steps and the error still exists, we must move on to the next steps to check the speed sensor itself.
Speed Sensor Plug issue.
If you did the previous test for both the magnet and the sensor, and the result was that both of them working properly, but the error 21 is still present, the problem may be in the speed sensor jack itself, or in the place of the connection in the controller.
In order to solve this problem, you must make sure that the speed sensor is connected well to the controller.
You can also make sure that the controller can read the signal from the speed sensor by using the ebike tester.
Internal Switch issue.
Inside the speed sensor, there is a switch that opens or locks the electrical circuit when the magnet passes in front, and the ability of the switch to work can be confirmed by the previous test of the speed sensor.
In the event that there is a problem with this switch and it does not work efficiently, the speed sensor should be changed