SpeedofLite 

Before I go to the Swap and Trade sticky thread, I thought I'd post this here since I'm a little confused about Flight Deck component version compatibility.

I'm replacing a right DA 7801 STI control lever on a friend's rarely used back-up bike.
He has a nice Flight Deck attached that he said used to work, but hasn't worked all that well since the original display head broke and he replaced it with a new one.
He said he thinks all the functions work, but he couldn't say that about the gear selection features.
Either way, he said he didn't want the Flight Deck anymore anyway as he uses Garmin and his phone exclusively now.

Anyway, his Flight Deck system consisted of a SC-6501 display head attached to a SM-SC70 mounting bracket/wire harness. The wires going to 7801 STI levers.
From what I can see in Shimano tech docs:

1. The 10s Flight Deck display head (SC-6502) only works with the SM-SC70 bracket/sensor unit and 7800 STI control levers.
2. The 9s Flight Deck display head (SC-6501) requires a SM-6501 bracket/sensor unit, but works well with numerous STI controls none of which are 10s.

Well, I think component compatibility is the culprit for the Flight Deck not working now. I think he should have purchased the 10s SC-6502 display head instead of the 9s SC-6501.
On the bench, the STI lever buttons don't affect the display screen. I checked continuity of the harness wires between circuit boards at the levers and metal contacts on the brackets, so there is no break in the wires.
If your experience with Flight Deck suggests I missed something, please let me know.
Either way, I know I need replacement waterproof caps on the STI lever bodies since I don't want to cut wires from the Flight Deck caps.
I'll look to swap one or more of the Flight Deck components I took off my friend's bike for these caps, plus maybe some cash.