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Ultegra DI2 upshift issue

On an otherwise normal stretch of a ride, my Ultegra rear mech (RD-6870) suddenly would no longer shift up, making 4-5 clicking sounds as if it was attempting to engage the servo to the cage, then quitting the process. Downshifts work flawlessly. I tried a crash reset (holding the junction box button for 5s) which led to the mech shifting down all the way to the 11 cog, and getting stuck there. Needless to say, it made for a good, fun ride back home against a stiff headwind.

Back at home, I did the following:
- disconnected battery, shifters from the junction, unplugged rear mech cable, ensured all were plugged back firmly
- connected to the e-tube app, checked all components are detected, connected, firmwares are all current
- ensured battery was charged
- took the rear mech from the frame, cleaned it externally, ensured there was no small debris or anything else which could be blocking the movement of the cage, put it back to the frame

The issue however persists.

A video of the clicking sound as I attempt to upshift:

In another forum I got reports of motors becoming "weak" since it appears to have lost the strength to move "up" (i.e. against the spring) - how does one go about testing/repairing/replacing this?

Any other obvious or subtle points I may be missing here?

Thanks in advance,

Posts

  • brundonbianchibrundonbianchi Posts: 654
    edited October 2020
    Have you checked that the hanger isn’t bent, and / or twisted, and that the L limit screw is set to allow the system to reach the big sprockets. Also make sure the angle of dangle is allowing the jockey wheels to clear the sprockets.
  • Hi brundonbianchi , thanks for the insight. The issue occurs even with the limit screws completely removed and with the chain taken out , that is, with the deraileur operating freely or being held in my hand. If I help the cage move (not a lot of force is necessary, just touching it with my index finger) , then it shifts up.
  • Hi brundonbianchi , thanks for the insight. The issue occurs even with the limit screws completely removed and with the chain taken out , that is, with the deraileur operating freely or being held in my hand. If I help the cage move (not a lot of force is necessary, just touching it with my index finger) , then it shifts up.

    Okay that sounds like a motor over run issue then. The mech is going past the position that the system has been programmed to recognise as fully extended. Run through the ‘index from zero’ / factory zero point routine. I don’t know what that is / how to do that on the Shimano system though.

  • pilot_petepilot_pete Posts: 1,979
    Have you got another derailleur you could swap out, just to ensure that works and the same problem doesn’t persist with a different derailleur? Maybe a mate’s?

    PP
  • @pilot_pete yes, I'm currently running the bike with another DI2 rear derailleur from another bike. Equally, the problem persisted when I put the faulty derailleur on the other bike, so it's very clearly an issue with the motor.

    Does anyone know how to open the motor bay? The screws have a weird triangular head and I couldn't get them open with neither a torx, allen or flat head screwdrivers.
  • You can buy triangle screwdrivers.
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