Everything You Need to Know. VanMoof SX3 Harness Loom
What is the Harness Loom?
The harness loom is a cable bundle that connects your bike’s electronics — motor, lights, brakes, sensors, and onboard computer. It runs internally through the bike frame. If it’s faulty, you’ll see a range of electrical failures.
Common Symptoms of a Faulty Harness Loom
Here’s what to watch for:
1. Intermittent Power or Display Dropouts
- Bike shuts off randomly or resets.
- Display goes dark without battery dying.
- Error codes that vanish after a restart.
2. Non-Responsive Kick Lock
- Kick lock won’t engage or disengage.
- App says it’s locked, but the wheel is free — or vice versa.
3. Front/Rear Light Issues
- Lights flicker, don’t turn on, or behave inconsistently.
4. Motor Cuts Out While Riding
- Boost button stops working.
- Bike suddenly rides like a regular, non-electric bike.
5. Inconsistent Light or Sound Level
- Sound features or front/back light are responding weirdly.
6. Multiple Error Codes (1-21, 44, 45, 48, etc.)
- Errors related to communication between control modules.
Step-by-Step Diagnostic Guide
Step 1: Check Firmware & App
- Update the VanMoof app.
- Ensure bike firmware is current.
- If issues persist after updates, move on.
Step 2: Inspect Cable Damage
- Gently move handlebars side to side — see if power or lights cut off.
- Perform reboots with different positions of handlebars.
Step 3: Run a Soft Reset
- Hold power button 10+ seconds to force restart.
- If the problem returns consistently, it's likely not a software glitch.
Step 4: Observe Patterns
- Is the issue temperature sensitive (heat or cold)?
- Does rain or moisture worsen the symptoms?
When to Suspect the Harness Loom Specifically
If you’re seeing multiple symptoms from different systems (motor + lights + lock), and they come and go, it’s almost always a loom issue. The internal cables may be pinched, frayed, or suffering from a poor factory connection.
Pro Tip for Technicians
Use a continuity tester or multimeter on both ends of the loom (if bike is disassembled) to test if any wires are broken internally.
Final Advice
If you suspect a harness loom issue:
- Document symptoms with video/screenshots.
- Avoid riding if motor cutouts are sudden — it’s a safety risk.
Solution: Harness Loom Replacement
Before you start.
Please watch the X3 S3 Wiring Harness replacement video to assess the scope of work required:
For New Wiring Loom Installation:
Always take these extra steps before installation for optimal performance:
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Remove all plastic zip ties to ensure the cables are free and flexible. If you use V2 of the harness loom, please keep a wide black zip tie that keeps the motor cable near the Smart Unit socket.
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Remove the sleeve from the motor cable to free up all the internal cores.
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Apply a high-quality electrostatic lubricant across all cables, but be cautious to avoid getting lubricant into the sockets. As an alternative, Tesa 4818 can be used for cable friction protection.
- (optional) Use dielectric silicone to hold/fix cables near the socket.
- (optional) Use fibre/kevlar tape to protect cables in sensitive areas (no adhesive version).
These precautions will help ensure a smoother and more reliable setup.
How to unscrew Wiring Loom main screws
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Use good quality tools
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If there is a 'screw stripped issue' - how to deal?
https://www.instructables.com/5-Ways-to-Remove-a-Stripped-Screw/
Remove all sharp cable transitions
Polish sharp edges inside the fork:
Restrict fork ability to turn far left and far right
A wider version of the original fork’s bold can be used to prevent deep turning left or right. This step significantly reduces the chances of the harness loom issue repeating in the future. If you have a 3D printer, a specific adapter can be used (original bold should be replaced with a countersunk M5x20).
What else can be helpful?
- A bike stand
- 3D printed tool to hold a battery socket: can be downloaded here
- Specialised tools to reroute the cables:
Other photos
