Electric vehicles can experience various malfunctions during operation, with motor failures being particularly common. Examples include motor wires breaking at the shaft end due to collisions, damaged Hall sensors, coil damage, magnet damage, and burnt motor wires.

Some motor failures are rare, while others occur frequently. Today's case involves a driver who, under the influence of alcohol, collided with a curb stone, severing the motor wires at the axle head. The vehicle immediately became immobile and impossible to push. How should this situation be handled? Is it repairable?

01 What faults occur when an electric bike motor wire is severed?

The intoxicated rider lost control, veering into a deep pit beside a curb stone. The motor tire punctured, and the motor wire snapped. After attempting a makeshift repair, the bike could only jerk forward briefly before stalling, and felt unusually heavy when pushed.

After towing it in, we first used a Hall sensor tester to detect abnormal motor Hall sensor operation and irregular phase lines. At this point, we need to disassemble the motor to further inspect its internal condition.

02 How to Properly Disassemble, Install, and Repair a Motor

1.Disassembling the motor: First, unscrew the screws holding on the front end cover, which is connected to the motor cable. After unscrewing the cover, do the most important part: gently tap the edge of the drum cover with a small hammer. Why tap? What purpose does it serve? Some repair technicians ask if this might crack the drum cover, since it's made of aluminum and heavy impacts could break it.

The purpose of tapping is to loosen the cover, making it easier to remove the motor stator. The factory-produced drum cover has its inner edges sealed with adhesive. Without tapping, there's a risk of cracking the cover when removing the stator. The result of this would be counterproductive – not only would there be a loss of money, but there would also be a requirement to replace the cover.

Use a small hammer to gently and lightly tap it. The tapping of each segment around the screw line once will result in the loosening of it, allowing for the easy removal of the end cover and stator.

After tapping, secure the screws at the opposite end of the motor to prevent damaging the shaft threads. Put a wooden board under the board you are working on to protect it. You don't need to use screws. If you don't have a board, just tap the motor lightly against a hard surface after you've tightened the screws.

When tapping, hold both ends of the motor firmly and tap several times to loosen the top cover plate.

Step 3: After loosening, position your hands slightly toward the edges. Keep fingers away from the end cover's rim to prevent injury if magnets attract your hands during impact. Apply more force while tapping, simultaneously pushing downward with both hands to better separate the stator and rotor.

If the bearing ring is not rusted, a few taps should suffice for separation. If rusted, vibrate it several times and apply more force to separate. Remove the stator and clean any rust found on the magnets.

2.Hall Sensor Disconnection and Connection: If the sensor is damaged, replace it. To do this, remove the wire clip. Then remove the adhesive backing paper. Finally, remove the sensor itself. Handle with care. This will help to avoid damaging the coil's protective coating. Damaging the coating could cause a short circuit. The Hall sensor should be gently pulled straight out from the mounting legs using pliers. If resistance is encountered, the mounting terminals should be tapped lightly with a small flathead screwdriver to release it.

Step 2: Thoroughly clean all adhesive residue and debris from the mounting area. Insert a new Hall sensor. If it slides in smoothly, proceed. If not, further cleaning is required.

Step 3: When inserting the Hall sensor, note the original phase angle on the circuit board. Some motors use 60 degrees, others 120 degrees. This must be verified; otherwise, the motor won't run properly.

Some controllers are universal, while others are intelligent sine wave dual-mode or triple-mode types that can self-learn, making them very convenient. Some original controllers labeled as intelligent cannot self-learn, requiring repeated adjustments to function properly. Be meticulous during installation. Once understanding of this has been achieved, connection according to the original wiring can be carried out without issues.

Step 4: Identification of Hall Sensor PhasesPrior to the removal of the old sensor, the orientation must be noted: three faces facing up indicate 120 degrees, one centre face down, and two side faces up indicate 60 degrees. If you overlook the phase angle during removal, verify it during installation. If the circuit board lacks markings, refer to the controller. If the marking is 60 degrees, set it at 60 degrees; if it is 120 degrees, set it at 120 degrees.Follow the identification method described earlier during installation. If the controller's marking strip is missing and the phase angle cannot be determined, install at 120 degrees. After installation, adjust the phase angle at the controller connection point.

Step 5: Secure the Hall sensor and wiring. Few circuit boards have built-in Hall sensors; most repair technicians use standalone three-wire Hall sensors. When connecting, ensure the wires are correctly identified. The securing of the Hall sensor is to be done using 502 adhesive or similar glue. The next step is to twist together the three red wires (positive terminals) from each Hall sensor and twist together the three black wires (negative terminals). First, cut the original red and black wires, then connect the new red wires to the positive terminals and the new black wires to the negative terminals. Therefore, the yellow, green, and blue wires should be connected in their original sequence as arranged on the circuit board. After completing the wiring, prepare the insulating paper pads.Attach it with adhesive and use zip ties to fasten the connection wires before installing it.

Once the Hall sensor is replaced, the next step is installation. How to install it? Let's look at the specific steps.

 Motor installation: Certain techniques are essential to prevent damage to the magnets and windings, and to avoid injury to your hands, during installation. First, firmly grasp the stator shaft with one hand. Hold the outer edge of the rotor with your other hand — never place your hand inside the rotor to prevent contact injuries.

Next, keep the rotor end stationary. Tilt it upright and hold it firmly. With your other hand, gently guide the stator into the bearing bore. Rotate it as you insert it to allow gradual entry. Once most of it is inside but a small portion remains, proceed as follows:

Grip the outer ends of the bearing ring firmly with both hands and gently tap downward. This action will press the upper cover and stator tightly together, allowing you to proceed with tightening the screws. However, one critical point demands special attention during this final step: if not handled carefully, the assembly may become unrotatable. To prevent this, ensure the stator is tapped flat and snug before tightening screws diagonally. Failure to tap the stator level—leaving it tilted to one side—will result in an unrotatable assembly.

Step 2: Use the repair tool to test the Hall sensor's functionality. So, once you've got the Hall sensor detection port in the repair tool, just lift the motor off the ground and rotate it slowly. So, the Hall sensor indicator will show three lights. If they're flashing between two, that means 120 degrees. But if they're all on or off at the same time, that means 60 degrees. The functionality of the Hall sensor is indicated by the normality of the flashing pattern. Proceed to mount it on the frame and connect it to the controller for normal debugging.

03 Correct Wiring for Motor and Controller

This electric bike has been in use for several years and is equipped with an older semi-intelligent controller lacking self-learning capabilities. When reconnecting using the original wiring, it may operate normally if luck is on your side. Otherwise, you may need to try all 36 debugging methods until the correct phase is found for proper connection.

If the connection fails to operate normally, try the 36 debugging methods: reverse the two thick phase wires, leave the red and black Hall sensor wires unchanged, and swap any two of the yellow, green, and blue wires. If debugging succeeds, proceed normally; if not, continue debugging. Remember to keep track of the different sequences. Only when a specific phase angle is found will the vehicle operate normally.

Conclusion

When disassembling the motor, completely remove the brake system, including all screws and clips. After removing the motor screws, gently tap the motor and firmly grasp it to knock it out. Pull the Hall sensor straight out—do not pull it at an angle. Identify the Hall sensor's phase angle and ensure all wiring connections match the original layout. This will significantly reduce troubleshooting steps during reconnection.

When installing the end cap, ensure the stator and can are aligned level—never install at an angle. Tighten screws diagonally. After installation, verify Hall sensor functionality using a diagnostic tool before final assembly. During installation, route motor wires and controller connections according to the original wiring diagram. Test for normal operation; if abnormal, apply one of the 36 adjustment methods until functionality is restored.

The process of disassembling, installing, and replacing the Hall sensor involves multiple steps with numerous precautions. This detailed guide shares practical installation techniques for thorough reference.