Focus Impulse (Derby Cycle/Daum system) — no pedal assist despite walk mode OK

[timwelch]

This is probably very niche but I am trying to avoid another ebike going to landfill.



I picked up a Focus Thron with an Impulse motor system that was dead - with the owner having taking it to their LBS and having them declare it uneconomical to repair. I suspected that the LBS knew they wouldn't be able to get parts if they looked at it and didn't want to be out of pocket.

I pulled it apart, cleaning up all the connections and put it back together. And it started working. I test rode it up the road and it appeared to be working absolutely fine to start with before stuttering on the pedal assist and then cutting out as I got back home.

I pulled it apart again and really can't see anything obviously wrong so put it back together and it turns on and off reliably but does not have any pedal assist now - which seems to be a totally new problem to what I started with.

Does anyone know on these bikes what might cause the pedal assist not to work but walk mode work fine?

 

[timwelch]

After watching several videos (in German) it would appear that these have a torque sensor buried deep inside them that is known to fail. Rust Massacre in the Impulse EVO RS
The insides of my motor look barely used so I'd be surprised if the torque sensor is at fault so I'll keep trying to diagnose wiring issues.