Di2 rear derailleur does not shift up


My Di2 rear derailleur stopped working properly. It shifts down without any problem, but once at the smallest cogs it only goes up one gear and then makes a noise like “tac tac tac”.
When resetting the derailleur by pressing on the button of the junction box the same happens.
The guy I usually take my bike to repair says he always recommends to change the part with this problem.
However, for me if the derailleur is capable of shifting up one gear it should mean it is not mechanically broken.
Does any one have any suggestion?

Plug it into the diagnostic tool should be your first port of call.

Make sure the battery is charged or hasn’t gone flat.

i’ve had this problem on my r8050 rear mech. The worm drive was cooked unfortunately.

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This… the ticking sound it makes means that it cannot move into the gear.

Usually this means that it’s blocked (limits set incorrectly, chain too short, etc.), but if the system has been working fine so far, then it usually means the RD has to be replaced.

If you take the wheel off and you ‘help’ It by gently pushing it in the right direction it’ll probably shift, but obviously that isn’t a real solution :wink:

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