josiah17

I've been fighting with the Di2 on my 2 year old Cervelo R3 for several weeks now and so far Di2 seems to be winning. In the middle of a ride a few weeks back it just started to respond only intermittently. At first the rear derailleur stopped responding but the front would still shift. That's opposite from the behavior when the battery runs low, and I had recently charged it, so it obviously wasn't a dead battery. If I stopped it would shift for me, but it gradually got worse. Eventually the front stopped responding too.

I don't have any other experience with Di2, but it's an electrical system with sealed components so the problem has to be with one of the cables or one the components. It almost always works when the bike is up on a stand. Riding with hands on the hoods often caused failure, so that pointed to the brake lever being the issue, which still seems to me the most likely culprit. I've tried riding with the brake hood pulled back and fiddling with the connection, and that sometimes worked. In fact, I replaced my junction A with a display unit that's meant for mountain bikes and you can see the screen flicker on and off when fiddling with that connection.

So that seemed to tell me I should try replacing the right brake lever. But I wanted to test the hypothesis first. In theory, if I removed the right shifter from the system and kept only the left shifter attached, it should work fine and only be able to shift the front derailleur. That would eliminate what I had diagnosed as a short or bad connection in the right lever. But when I did that, the left lever started behaving the same – only shifting intermittently and I could see the display flicker on and off. I find it hard to believe that both levers could have started failing in this same way at the same time, so maybe that is pointing to something else?

Di2 components are not exactly cheap, so I don't really want to just start swapping out components without understanding what's actually wrong. The last shop I brought it to said they opened the bottom bracket and replaced the cable between junctions A and B. I've replaced the cables between junction A and both levers. It's now been taken apart, diagnosed on the eTube software and put back together 4 times by me and 2 different shops, each time with the same result – testing it on the stand and riding around the block a few times it seems fine, but a few miles into my next ride it stops responding again.

I'm pretty much about to tear my hair out or ditch the bike at this point. If anyone has experience with Di2 and could offer any ideas, I'd be happy to hear them.

Thanks!

Rogerogeroge

I've had the first gen di2 for ten years (10 sp) and 11sp for about six years. My story all relates to the first gen - After about six years, the shifting would go out without explaination. It got progressively worse. I could actually bunny hop my bike a few times for several rides and that would seem to make it cooperate until it eventually totally crapped out. The culprit ended up being the junction box (EW-90), the one at the handlebars. The way we diagnosed it - friend had a totalled bike from being hit by a car so we hooked up his cockpit to my bike at the junction on the downtube. (We had also tried troubleshooting the components and wires past the BB, but I'd suggest start at the cockpit). Ended up buying a new junction box for less than $100 (and a small risk that it wouldn't work), but all is good. Odds are your trouble is in the junction box, not the wires. Try to find a friend with the same setup and feed his setup from his handlebars into yours. You may have to take off a handlebar step on one of the bikes to get the necessary reach to connect everything to the second bike. My method won't definitetively tell you what's wrong, but it will narrow it between the front and back of the bike. And again, probably a junction box failure and not an e-wire failure.

BHG6

Try replacing wires before replacing components. Get one of the longer Di2 wires ($25) and then jump out any of the suspect ones. The wires are pretty well made but you can easily damage them by pulling on the cable without using the little tool.
Also, if they didn't leave enough slack in the wires when the bike was assembled, connections can become stressed when the frame flexes or when you turn the handlebars.

faulker479

I know you mentioned connecting to etube. did you try to re-assign shifting from one shifter to the other? AKA, did you try to have the rear mech controls moved to the left shifter and vice versa?

jadocs

I wouldn't replace anything yet. I would check all connection points for a tactile click when inserted. Battery, both derailleurs, both brifters, your junction box and wireless module if you have one. If it still acts up see if you can borrow a battery from someone you know who also has Di2 to see if you don't just have a battery that is on it's way out. I have seen a bad battery affect responsiveness of rear shifts, all the way up to the point where the entire system didn't work anymore. The bad battery still appeared to take a charge...when in fact it wasn't.

sch

On two occasions my Di2 has had one shifter, L IIRC both times, stop working. First when the bike fell over and the front
wheel was rotated enough that the bar hit the top tube, and second when I hit a very obnoxious bump with the bike tossed
upwards and my arms jammed into the brifters. On both occasions the problem was a subtle disconnect of the cable
at the brifter, due in part to "insufficient slack" ie no ~1/2" of extra cable curled under the hood. I fixed the first myself
by reseating the connector. The second time I thought for sure I had reseated, I used the tool felt the pop but still dead.
etube assessement showed I was wrong and the connector was not fully seated. Everything worked fine after positive
reseat. FWIW my oldest battery is from 2013 and still works fine, discharging to ~40% after 500-600 miles of riding and
my brifters are the original 6870s now used with 11spd Ultegra Di2 deraillers.

First thing to do is expose all connections and reseat those buggers with the tool. Second is an etube assessment
by someone versed with using the software, it is not entirely user friendly.