Motor "stalls", "rattles" (ST2 / ST2S)

Symptoms

• A loud noise, locking of the rear wheel and almost impossible to move.
• There is also an unusual rattling noise when braking - if the brake is pulled as far as it will go, there is a noise when it is released and the result is a jerk forwards.
• As soon as you accelerate in operating modes 1/2/3, it rattles violently and also brakes.

Possible cause

• Brake pads broken in the middle and therefore displaced. This causes them to become jammed in the brake calliper and press on the brake disk.
• Motor cable defective or solder joint on the plug defective. The problem occurred especially with the ST2 / ST2S. The cable runs through the left chain stay and is connected to the controller (MCU = Motor Control Unit) via a plug connection. Before replacing the cable, you should check the solder joints in the HIGO connector. These are often the problem. The part number of the entire cable is 221244 (ST2 / ST2S).

If necessary, you can continue driving at a moderate speed when the fault occurs. Drive slowly, accelerate slowly until the supposed blockage occurs, then reduce speed again.

The function of the motor can be checked with the SIT (System Integration Test) must be checked.

> See ELEKTRIK / ELEKTRONIK - Testing / Pürfen - 'SIT (Test Runner) - Testing components'
> See also ERROR MESSAGES / WARNINGS - 'E 21020E | Support problems'