Di2 RD intermittently not working

[beantownjjj]

Hoping to get some ideas on this ... recently had LBS convert my wife's Parlee Altum from mechanical group to 11-speed Di2 (6870). However, the rear derailleur seem to be cutting out intermittently. Seems to happen after bike sits idle for a while. Press either up/down shift buttons and nothing. However, when holding for a few seconds, battery indicator light goes on. Front derailleur working fine and actually going up/down on big chainring seems to "wake up" the RD. Took it back to LBS and they upgraded firmware and ran diagnostics -> all green. Also checked cable connection at brifter and seemed fine. Not sure where to look next - maybe cable from junction B to RD? Any ideas appreciated!

[KJMUNC]

Sorry to hear….I finally figured out the best way to fix all my di2 problems: I went back to cables

[robt57]

Originally Posted by KJMUNC

Sorry to hear….I finally figured out the best way to fix all my di2 problems: I went back to cables

Come on now, how is that helpful?

I suspect a plug not in completely or other physical conectivity issue.

Like to see e-tube connectivity check result.

[oldpotatoe]

Originally Posted by beantownjjj

Hoping to get some ideas on this ... recently had LBS convert my wife's Parlee Altum from mechanical group to 11-speed Di2 (6870). However, the rear derailleur seem to be cutting out intermittently. Seems to happen after bike sits idle for a while. Press either up/down shift buttons and nothing. However, when holding for a few seconds, battery indicator light goes on. Front derailleur working fine and actually going up/down on big chainring seems to "wake up" the RD. Took it back to LBS and they upgraded firmware and ran diagnostics -> all green. Also checked cable connection at brifter and seemed fine. Not sure where to look next - maybe cable from junction B to RD? Any ideas appreciated!

I'm not a Di2 expert but things like that often sound like a connector problem, since it's intermittent..I'd start there. Either at the rear der or at the 'junction' box or the RH shifter, the interface. Like 5 connectors(more) that could effect this.

At 'c' or 'e'...generic diagram of Di2.

[charliedid]

Yeah all those plugs. Start with the right shifter...I always pulled a plug out because I mess with fit and adjustment too much....or did.

Pull back the hood and take a look. Having one of the plastic plug tools is needed but you can make do.

This sort of helpful answer brought to you by one half cup of coffee.

[accordvsick]

Can you replicate pretty easily?
If yes I would try wiggling the cables to see if you can get them to cut out once they are 'connected"
You can also remove Rd and temporarily plug into the front derailleur spot to see if the problem happens.

Intermittent electrical problems are a pain unfortunately.


Guessing you got these used?

I'm running the same Rd setup and I love it. Converted last year.

[jemoryl]

I don't have any specific experience with Di2 (still like mechanical...) but you might try using a contact enhancer like De-oxit on the connectors. Very useful for noisy switches, dodgy connectors with audio and other electronics.

[caneye]

Does the intermittent issue arise mid-ride when idle - eg cruising or free-wheeling?

Or strictly only when the bike is left idle for hours/days?
I sometimes have to press the shifters multiple times to wake the system up if bike had been left untouched for a few days.

Maybe it's just me, but if left idle I find it very rare if not impossible for it to shift from the first touch

Otherwise ..
- as mentioned , check the connections, use the proper DI2 plastic tool so you pull/push on connector instead of cable
- depending on your DI2 junction box, you may be able to troubleshoot via E-tube software

Good luck.

the one derailleur I had that encountered intermittent connectivity issue did stop working after a few months (after 8 yrs of service).

[fogrider]

try new cables, while they're not cheap, seems like a good place to start.

[AngryScientist]

Boston is a cold damp place this time of year. I’d pull all the connections and use dielectric grease in the connectors. Inspect them closely for corrosion and proper contact.

I know zero about how di2 wiring works; but continuity checks on the wires would probably be the next troubleshooting step.

[deluz]

This happened to my wife’s bike. Took awhile to figure it out, but re-plugging the connectors on the junction box located at the BB permanently fixed the problem.
There is an access cover under the BB so it turned out easy to do.

[beantownjjj]

Thanks everyone for the input! I'm going to start by checking all connections myself - great tip about the bottom bracket access hatch - I was thinking I might have to pull the cranks/bb out!