(EDIT) non-relevant advice below...only applies to E-tube/modern Di2. This thread is all about first gen.


The 'system' really lives in the battery, so replacing that should take care of anything. I doubt a little moisture there would short out other pieces.

Good troubleshooting...

1. upgrade the firmware of everything
2. connect the battery to just a shifter and one derailleur.


1. if that works, add one thing at a time to find the culprit
2. if not, try the other shifter and derailleur (and if possible, other cables)

OK cool, will try that. Do I need a special tool to disconnect the cables?

Disregard the info on battery being the brain and any reference to firmware. Gen 1 Di2 is not controlled by the battery as the derailleurs have the smarts and shifters are dumb switches. Also Gen 1 Di2 does not allow for firmware upgrades.

Disconnecting the derailleurs is helped with the gen 1 di2 tool, but you can manage it without. Be sure they are both clicked in completely. Your battery is likely not the issue. It sounds more like a junction/harness failure since both derailleurs are down. The RD is notorious for dying permanently, but the fronts are usually solid.

Downside is that taking apart any Gen 1 harness requires cutting off heat shrink tubing at every plug. And it would be tough to find any shop that still has the Gen 1 component testing unit. There are replacement harnesses available at times on eBay and from some retailsers. Troubleshooting Gen 1 wo extra parts is going to be difficult.

 
Had a similar problem 2 years ago with 1st gen Di2. Broke a shifter, took to LBS thinking they would just change it but when they plugged it in everything started closing down. Apparently because the firmware hadn't been updated in a couple of years they had hell of a problem updating (and ultimately couldn't), and after plenty of advice from Sheppards ended up having to purchase new rear mech and shifters.

Interested to hear how you get on and what the fix is.

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Thanks for that info. I guess it’s unlikely that both the FD and RD have failed, so a safe bet it’s the harness?

Harness issue would be my best guess. When one of my RD’s failed it would still respond to crash mode reset. This is triggered by holding the junction box button for approx. 10 secs. Worth trying to verify harness isn’t functioning.

If it is the harness/junction you’ll need to figure out what combo was used on your bike. There is only one front harness if using the TT configuration. This is the one I’d consider swapping out. There are several rear harnesses with external and internal models of various lengths. I think there may only be one internal model, but this is from memory.

So really if I've replaced the battery and it's still not working, the problem is going to lie with either the harness or the part the battery plugs into (see below) or a damaged cable. This was where I saw the moisture, on the inside of this part.

Call around to some LBS and see who has a gen 1 di2 tester. They can hook it up to the system and see where the problem is.

The battery and holder in that set up are pretty bulletproof. It has to sit out exposed to water. The problem with the Gen 1 DA 7970 version of that holder is it is hard wired into part of the rear harness system I mentioned above, while the new version you linked works with e-tube wiring and can be swapped

Finding a Gen 1 tester would be rare. Most bike shops hardly even carried 7970 Di2 and by the time they caught up things had moved to Gen 2 and e-tube. If you know anyone else with 7970 near you it would be quick to check your derailleurs on their system to verify they work and the fault is elsewhere.

Also worth checking the one connection point on the Di2 harness that isn’t heat shrink enclosed. It is on the frame side wire of the junction box control. There is a connection where the front harness snaps into the rear harness. Again, the Di2 connector tool helps a lot for separating this connection. But u can prolly do it carefully by hand or with small pliers.

I just spoke to the bike shop and he seems to think it's the front harness. He said jiggling the wires he can sort of get it to work. He said these harnesses are as rare as hen's teeth, but there are a few on ebay. I asked if they were easy to fit myself, but he started going on about the wiring being really tricky and it doesn't sound like an easy job?

Have them check all the front harness wires between the extension/bullhorn junctions and the control junction. I KO’d my wife’s Di2 at 2015 Whistler after pinching one of these wires between the bar and proprietary stem on a SC. We were sure the torrential rain had killed the Di2, but it was the pinched wire. After freeing it the system worked again and never stopped working.

If a damaged section is found it can be cut out, resoldered and sealed. With dumb shifters and only two conductors in this wiring things are pretty simple. Actually the worst part of that system is disconnecting the connections with glued heat shrink.

What sucks is that planetcyclery.com was offloading those sm-ew79ai harnesses for years until they recently sold out. They are still selling off the road versions, but that won’t help here.

Yeah my bike is a road bike. I'll take some photos when I get it back from the bike shop. So assuming it's the front controller and/or wires, all I would have to do is buy the road version of sm-ew79ai and that will come with the wires which I can just plug in myself or will I need to do soldering myself?

If you get new wires there is no soldering needed. There is just a length difference when it comes to the harness to the RD, I had to change that and there a differences from half an inch, so check the exact number before ordering new (if you are lucky), on mine there were a „/2a after the regular number if I remember correctly.

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-shoki

That makes things much easier. The road version of this harness (SM-EW79AE) is really just a Y-harness with a junction box controller inline. So two plug ends, one for each brifter, plus the connection I described earlier that links the front harness to the rear harness. With this configuration you do not even have to deal with the glued on heat shrink as that is only on the rear harness.

Here is the sale link I found: https://www.ebay.com/...b:g:ltoAAOSwvoNblqq1

Thanks for that. I'm in Australia. Not much (like nothing) availability here. Will order from USA if need be. A bike mechanic mentioned to be it could be upgraded to a newer version. Is that right or is the SM-EW79AE the only one I can use?

I found this listing on eBay Australia: https://www.ebay.com.au/...arness-/123746136286

None of the first Gen Di2 can be upgraded. The only option is replacement to newer systems.

awesome thanks heaps for your help