renouj21

Hi there,
My Di2 front mech has stopped working. At first I assumed it was the battery running low, but it's now fully charged and no sign of action. I've checked all the cables, they seem to be properly engaged. When I press and hold the front mech shifter no light comes on at the junction box (but it does with the rear shifter). My shifters are the R785 units (for hydraulic disc brakes). Are there any further checks or actions I can take before handing it over to my LBS?
Many thanks

gsa103

Can you swap the front and rear shifters at the junction box? That would isolate the issue to a bad shifter or a bad derailleur.

fietsbob

Check wiring for continuity? is My input. online tech manuals must be out there..

I just fixed My Head/taillight set , by process of elimination , checking each part , separately..

I'd never buy a Di2.

wschruba

You need the SM-PCE1 to do any diagnostic work on Di2 components. Without it, you're just guessing (replacing wires, components, etc). As fietsbob said, you can use a continuity tester to do more than just guess, but to troubleshoot components themselves, you need to plug them into the tester.

Shops that work on Di2 should have it, though you can buy it yourself. It is an expensive investment for a 1 time fix, though...

renouj21

Good thought. Done that, the rear mech still works fine, the front mech not at all. That would seem to isolate the problem to the shifter wouldn't it (given that I can't get the shifters to trigger the battery light on the junction box)?

rm -rf

You get a solid green light at the junction box when holding the right shifter? Then it's not a battery charge problem.

I would unplug and replug the wire at the shifter and at the junction box. The connector has to click in.

I liked the left-right shifter swap test, but I actually don't think it will work. The stem junction box doesn't appear to have predefined left/right connections--I think it just merges the signals onto one wire. The left and right shifters probably have differently coded signals. And see this weightweenies thread--he connected the right shifter to the left, then the left to the junction box, so it must be coded signals from the shifter.

The wire is probably okay, it's pretty sturdy. (I unscrewed my rear derailleur from the frame to check the dropout, and forgot to unplug the wire. It popped off with no damage when the derailleur dropped down.) But if you aren't sure, you could pull the right side wire and try it. You'd have to unwrap the bars, of course.

The Di2 Dealer Manual is worth downloading. It's easy to understand, and covers the wire installation in detail.
Download from this page: Shimano Di2 dealers manual. Get the full set of pdfs for your groupset, especially the red DM-UL0001-02 pdf.


From the Park Tool Di2 installation guide:

Your bike should have come with this Di2 wire installer tool. It makes it much easier to pull the connector and to push it back in--until it clicks. (sorry about the giant photo)



The shifter wire needs to have a little slack at the shifter instead of being stretched tight there. This is probably the minimal slack, the dealer manual shows a bigger loop/bend here.


Let us know what the unplug/replug does for you.

renouj21

My shifter is a little different, because it's the hydraulic brake lever. Not easy to get that cable out at all (I don't have the tool), it doesn't look like it's come loose. But I've done the cable at the junction box, and that's not made any difference. I guess it's the bike shop for me.
Thanks for all the suggestions
J

rm -rf

You want the DM-BR0004-04 pdf manual from here. See pg 43. check the drawing there to see if it looks like your cable is clicked in all the way.

It clicks in just the same way as the photo above. The tool's hook end fits in the groove on the wire connector head to pull it out, and the tool's barrel end makes it easy to push the connector in.

renouj21

Hi all,
Took it in to the bike shop, it was the cable connection at the lever, as predicted by some of you. I couldn't get at it without the special tool.
Thanks for taking the time to try and help.
J

L Arnold

Well, Unplugging and replugging just now worked for me. Thanks for the tips there guys. Seems to need a shove more often than I would like ( Twice after the replug) May need to make an adapter like the special tool above. Hope I don't have to resort to tape to keep it there.

Good thing now is I have 2 batteries. Better try to wear them both out some weekend.

momoman

THANK YOU! THANK YOU! THANK YOU!

On my ride on my Wilier Gran Turismo yesterday my front derailleur didn’t shift at all. I had installed a 1st gen. Ultegra 6770 Di2 set last year that I bought off a friend who was upgrading. It worked flawlessly for over a year then the FD failed to shift yesterday. I searched on Google and this thread came up.

One of connectors at the brifter had worked its way loose. I clicked it back in and it works now. I guess I didn’t give that cable enough slack when I wrapped the bar tape over it and the cable must have been pulled loose from gripping the bar tape and rotating it as I was riding.