Knowledge base
Current
Possible causes
- Over-current (short circuit, stalled motor)
- Faulty current sensor in the controller
- Phase short in the cable
Safe test steps
- Free wheel rotation unpowered; phase cable damage.
- Phase resistance symmetry without the controller.
Workshop reference values
- No general documented measurement value – manufacturer service documentation required.
Repair approach
- Remove the short; if it repeats, check/replace the controller.
Tools needed
- Digital multimeter (CAT III, fused inputs)
- Basic hand tools, insulated screwdrivers
Safety
- Do not repeat the test if the controller heats up or smells burnt.
Related verified fault codes
| Code | Meaning | Component | Reliability |
|---|---|---|---|
| Bafang 12 | Current sensor fault in the controller | Current | Per manufacturer documentation |
| Bafang 27 | Over-current in the controller | Current | Per manufacturer documentation |
| SW900 LCD 21 | Current abnormality | Current | Widely published – may differ by model/firmware |
| S866 LCD 21 | Current abnormality | Current | Widely published – may differ by model/firmware |