jnbrown

My wife's bike has Ultegra Di2.
We always put our bikes in the back of our minivan to go someplace to ride. When I took her bike out of the van and she started to ride the shifting was dead. The LEDs on the junction box do not light up when pressing the shift buttons.
So she rode it in a fixed gear (not happy). I Was going to try and troubleshoot it with a meter when I got home but then after taking it out of the van it magically starts working again. This has happedned in the exact same way 3 times.
Here are my thoughts:

Vibration while driving in the van is causing a losoe connection.
But then why does it start working after driving home?

I use a strap round the handlebars to hold it in the back of the van. Maybe the strap is pulling on the wires somehow?

I have checked the connections and also pulled the seat post to check the battery connections and could find nothing.

Maybe the junction box is bad / intermittent.

Has anybody else had a similar problem? Any ideas what might be causing it?

Thanks

cxwrench

Neither derailleur will work? What happens a LOT is bike builders don't leave enough slack in the wire at the shifter. People do all sorts of things when they ride or transport bikes. If you're attaching the strap in a way that could pull on the tape/wire that could be it. Has the bike gone down recently and then has the shifters straightened?
At the shop I would plug it into e-tube w/ the battery charger and see what the computer recognizes...that tells me a lot.

jnbrown

Correct, nothing at all works, bike has never been dropped.I am thinking it is not the shifters because neither shifter works and the LEDs on the junction box are dead. So both shifters would have to have a connection problem at the same which I think is unlikely. When it does magically start working, both shifters work. But I will check those connections since it does seem related to the handlebar strap.
I am thinking it is a bad connection to the battery at some point. I have read that the problem could possibly be junction boxes inside the frame.
I am an electrical engineer but not a Di2 expert. Thanks for the help.

cxwrench

Have someone (shop) plug it in and see what happens. You can plug the entire system in and then if some components don't show up you can go to single component mode and plug directly in to every individual part of the system and check them for faults that way.

cpach

If it's a recent (actually, at this point, just not super old)version of Di2 with a charging port on the A junction box that uses a charging cable with a USB connection on the end, you can use your charger to connect it to a Windows PC, and Shimano has the eTube software free for download at https://e-tubeproject.shimano.com/application/ . Wouldn't hurt to update firmware and run the diagnostic. The only thing a shop might have is the SM-PCE1 which lets you plug individual components in by their di2 wires to diagnose them individually.

To me it sounds like a connection problem, which is often but not always caused by insufficient cable length somewhere, usually between the shifters and the A junction box.

Le Mechanic

If the whole system is shutting down intermittently, from what I've seen the issue is a bad connection from the battery to the B junction or the connection from the B junction to the A junction. Those are the only 2 wires (assuming you have a typical set up with the A snd B junction boxes) that run power through the entire system, so if everything shuts down (no LED's, no response from either shifter, Etc), you can pretty much isolate the issue to those locations.
If the battery or either of the junctions themselves are bad, typically it's not intermittent, it just won't work period. I've installed, diagnosed and serviced 100's of Di2 systems since their inception on a wide variety of bikes. From my experience, with the issue you describe, 10% of the time it's a damaged wire and 90% of the time the wire from the B junction to the battery isn't FULLY plugged into the battery. It has to be plugged in to the point where you hear an audible click or pop when it's in all the way.

jnbrown

I really can't see how it can be the shifters because both shifters would have to be disconnected at the same time. I can disconnect one shifter and the other shifter still works and shifts the derailleur. If it is the B junction box then that is inside the frame? How do I access it?
Do I have to remove the crankset? This is on a Cannondale Synapse with BB30 bottom bracket. I believe the charger does have a USB connection so I could plug it into a computer. I have already pulled the seat post and checked the connection to the battery. I am going to keep my meter in the van so I can check the battery voltage at the junction box mounted to the stem in case this happens again on the road.

Thanks

cpach

Try the computer first because it's easy and noninvasive. The B junction box sucks to get to. The standard place to put it is in the downtube in front of the BB, and getting to it requires removing the crank and BB, but sometimes it'll get put somewhere different, like in the seat tube.

jnbrown

I am a pretty good bike mechanic having worked on my own and others bikes for 45 years, but pulling out BB30 bottom bracket bearings is something that is not in my skill set or want to try. The Cannondale manual shows an access hole in the internal BB shell, but not sure easy it would be to get to the B Junction box. Maybe I should ask Cannondale.

I did notice in reading about the A Junction box that there is a button on the bottom that can put it in Bluetooth mode so I could use it with E-Tube on my Iphone if this happens again on the road. It also lights the LEDs so it would tell me if the battery is connected or not.

cpach

To my knowledge (am a little behind on some Shimano training right now) all of the road Di2 systems need a D-Fly inline bluetooth adapter to use a bluetooth connection--most bikes don't ship with this.

Le Mechanic

No, not sure how you got a shifter issue from my response? It's either a damaged wire from either the wire running from the battery to the B junction or the wire running from the B junction to the A junction, or one of the 2 wires isn't plugged in all the way. Since you say you have a tie down of some sort running across the stem, the A junction connections seem a little suspect. Check to make sure all the wires are plugged in and not damaged at that location.
Lots of old school bike mechanics are not super familiar with BB30/PF30 BB and crank interfaces, as well as electronic shifting issues, so there's no shame in taking it to an experienced shop to sort it out.

TerryDi2C

Yep - the manual for the SM-EW90 / EW-RS910 sometimes suggests otherwise (or at the very least does not mention this requirement), but yeah - on current gen Di2 bikes you'll need an EW-WU111 / EW-WU101 or an MTB display to enable bluetooth.

Iride01 

What happens when you push the button on the junction box? If you get a light, then what lights?

There is probably a Murphy's law for coincidences of your Di2 battery being too low to shift the front DR and your rear DR being in crash mode. If that's the case, then hold the junction box button for more than five seconds and then try the rear DR. Not the front as it won't work if the battery is too low.