E-Bike Motor Repair – Damaged Cable Bafang Hub Drive

E-Bike Motor Repair – Damaged Cable Bafang Hub Drive

!!! Make sure to read the pinned comment from Mels van Hoolwerff below !!!

This video gives an overview of how to fix a Bafang rear hub motor when you’ve got damage where cable enters the hub.

Before we get into the repair itself, let’s see how the problem shows up. The first sign of trouble on this e-bike was that the information display stopped showing the speed and started reporting error code 21. The manual for the C961 display tells us that error code 21 is for “Speed sensor abnormality”. Over the following weeks, another problem emerged – the power would cut off regularly and the e-bike would not work until the bike was turned off and on again. It seemed that the bike was particularly prone to losing power after going over bumps in the road. Finally, as you can see in this picture, the wire bundle coming out of the motor appears to show some damage. Putting all of these clues together, we can be pretty certain that damage to the wire coming out of the motor was causing problems.

Now for the fix. Make sure to take lots of photographs as you go along so that you’ll know how the motor goes back together. Remove the wheel from the bike, and take off the cassette. You’ll need a cassette lockring tool with a decent-sized hole in the middle so that it can slip over the cable coming out from the hub. Next, remove the six screws around the outside of the hub. These screws have strange heads, a bit like a Torqx head but with a little pin in the middle. Once the screws are loose, the motor should slide out of the hub. You will also need to remove three large screws and the circlip that hold the metal gear wheel onto the motor. I made the mistake of also removing the six screws that attach the freehub body to the end plate. These screws were so tight that I stripped the heads of three of them and had to drill them out. I should have allowed the penetrating oil to soak in for longer. As it turned out, removing the screws was an unnecessary step anyway. Learn from my mistake and leave the six screws around the freehub body in place.

Instead, unscrew the two axle nuts and simply slide the freehub body off the motor. With the freehub body removed, three more screw heads become visible. Remove these and pull the cable through the axle to reveal the point where the cable was damaged. Cut the cable below this point with a wire cutter. The cable contains nine wires. The three large wires (green, blue and yellow) carry three phase electricity to make the motor turn. The other six wires are for the various sensors inside the motor. The red wire is +5V, the black wire is 0V, and the other four wires carry signals.

De-solder the six old signal wire ends. Next, with the old wire ends out of the way, strip the new ends and solder them into position. Originally, the signal wires were soldered in from the bottom of the circuit board. However, it is not easily possible to remove the circuit board so it’s probably best to solder the wires in from above as shown here. Be as neat as possible because there isn’t much space to work with here. Next, join the three main power wires. Use some heat shrink to protect against short circuits. And there it is, the cable is fixed. And now with some new screws to replace the ones that I had to drill out, the repair is complete and everything is ready to go back together. But before you do put your motor back together, it’s worth taking the opportunity to clean and lubricate the moving parts. And, with everything re-assembled, the is e-bike back in action.

One more thing to note is the way that you position the cable when you put the wheel back on the bike. Make sure to route the cable out of the axle in so that it passes through the notch in the side of the axle. This way the cable is less likely to get damaged if the bike falls or gets hit from the side. This motor might not have needed to be repaired in the first place if the cable had been installed this way from the beginning. And be careful about using panniers because the weight of a pannier resting on the cable could damage it over time.

Thank you for watching.

Readers Comments (20)

  1. Thank you, Dominic. Great Tutorial!

  2. Mels van Hoolwerff December 23, 2020 @ 9:57 pm

    They way you installed it will cause rain to drip into the motor and then everything will rust inside and probably the clutch will brake at first. I can tell you from experience. Better to use a longer cable and put the axle upside down.

  3. Thanks for the video..Where do I get an electronic board like the one in the motor on which the six wires are attached. Can you provide me with a specific site link?

  4. Hi I have a new ebike kit wheel wont turn when any phase wires touch each other when not o bike or power connected when all set up wheel wont turn feels jammed thanks if you can help

  5. Hi. How does the rotor not scratch the stator, under the weight of the rider and bumps?

  6. Jeremiah Mcintosh December 23, 2020 @ 10:10 pm

    Great video thanks for sharing! Also great tip about the panniers!

  7. New subscriber here.

  8. Good video, thanks.

  9. Is problem motor hub power is gone and work. how is repair?

  10. hello DOM I BOUGHT A BAFANG 8FUN 250W HUB OF A GERMAN COMPANy THEY HAVE NOT BEEN HELPFULL AS IN TAKE THE MONEY AND RUN IT HAS 6 PINS ON IT 3 THICK 3 THIN ITS SOMETHING I HAVE NEVER SEEN BEFORE I CANT SEEM TO GET A SPEED CONTROLLER ANYWHERE FOR IT AS I HAVE NO IDEA IF ITS SENSOR OR SENSORLESS CAN YOU HELP OR ADVISE MY FRIEND PLEASE ?? PICS AVAILABLE

  11. Not only informative, but a wonderfully produced video. Extremely clear voice-over with no distracting background ‘music’ — well done. The written transcript is just a great bonus. If you felt up to it, it would be great to have a companion video showing how to confirm your deductions about wire failures with an actual test of the separate wires in the Higo L9 connector! This is just me being greedy 🙂 There’s a great resource at https://www.ebikes.ca/learn/troubleshooting.html that is also extremely helpful in this regard.

  12. is the hub speed sensor inside this one?

  13. Good repair 👍

  14. do you think if you disconnected the speed wire it would disable it

  15. Very well documented, thank you Dominic.

  16. Very clear and nice video. Will the hall sensors with different series numbers will match all different brushless motor controller or there must be a mentioned hell sensors inside the brushless hub motor that can match a specific motor controller. Please advise.

  17. 🗽Nice work👍

  18. Where did you buy the cable ? Or the name of the cable . Thanks

  19. Excellent video. Thank you!

  20. Hello, nice video but I have a question. When you mention that you need cassete lock ring tool with decent size in the middle, how did you remove the original nut that is on the axle and holds it to the bike frame? When I unscrew mine it is still stuck on the power cable and can not be forced over the connector.

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