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  1. #1
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    Trek Madone/7900 di2 connundrum

    So I have a Trek Madone 7 series with the first generation of 7900 di2. My shifting goes out completely intermittently, which I'm 99% sure is caused by the connection between the cable coming out of the junction box and the cable that goes into the downtube and down to the bb.

    Searching on Shimano's tech site, I think I need the following junction box (SM-EW79A-E):
    http://si.shimano.com/pdfs/ev/EV-SM-EW79A-E-2969.pdf
    And I need either junction cable Y-7E0 98020 shown here (item #2)

    http://si.shimano.com/pdfs/ev/EV-EW-7972-2903.pdf

    or either the long or short junction cable shown here (also item #2)

    http://si.shimano.com/pdfs/ev/EV-EW-7973-2968A.pdf

    Can anybody confirm which part #s I need (I'm not even sure if I'm listing the numbers correctly) and most importantly, where can I find these items? It doesn't look like Shimano or QBP carry them.

    I did find a IEW7973B kit from Shimano b2b - it's evidently for an externally mounted battery (not under the bb like mine). Would this kit contain what I need?

  2. #2
    sgc
    sgc is offline
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    Just one observation, I had a very similar issue with the same system as fitted to an early Domane 5.9. The problem wasnt the actual cables, it was that water had gotten into the junction box itself and corroded the connections.

  3. #3
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    Did you do the installation yourself and if so did you use the tool to plug the cables in tightly? Had some intermitant issues with mine out of the gate and I just didn't have one of the cables in all the way.
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  4. #4
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    Quote Originally Posted by Srode View Post
    Did you do the installation yourself and if so did you use the tool to plug the cables in tightly? Had some intermitant issues with mine out of the gate and I just didn't have one of the cables in all the way.
    Top notch mechanic installed 6 years ago, and groupset is actually on its 8th season. I did unplug/replug some of the connections with the correct tool when troubleshooting. When I re-connected the one in question, it didn't shift and I had to re-connect it twice. I probably had 2-3 isolated instances late last year when it cut out one time only. Then about 4-5 rides ago it started happening more frequently, multiple times on each ride.

    So yesterday I unplugged the connection (with the tool), sprayed both ends with contact cleaner and dried with compressed air. Reinstalled (with the tool), and now I can't get it working at all. I do have a small 'tooth' mark on one of the fittings, but it looks like it only affects the outside of the connection, not the part that's next to metal. Don't know how it got there. I did go down hard on that side of the bike 2 years ago.

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