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Flight Deck erroneously jumping to smallest cog (ideas?)(7 posts)

Flight Deck erroneously jumping to smallest cog (ideas?)mleptuck
Jul 16, 2003 10:28 AM
I've got a Flight Deck 6501 head connected to a wireless sending unit on my Ultegra bike. About 2-3 rides ago, I noticed all of a sudden that the rear cog indicator was erroneously indicating I was in my 11, and not whatever gear I was actually in at the time.

All other functions are normal (speed, front ring indicator, time, and all calculated functions such as avg. and cadence), so I've ruled out a bad battery in either end of the chain (head or sensor sending unit). Like I said, it is only the rear gear indicator, and this problem is sporadic, sometimes the indicator will work for hours at a time correctly, then all of a sudden, according the the display, I'm stuck in 39x11 or 53x11!

When I change gears on the rear, the indicator moves to the correct gear, and proper gear-inch ratio is displayed, and then 2-3 seconds later, the indicator shoots back to the 11.

I was originally suspecting I needed to install the 'buffer' pad they give you to help push out the ribbon connector where it meets the button switch in the shifter hood, but I'm not so sure anymore, since my shifting works fine, and the head unit DOES display the correct gear, albeit briefly when I shift. 9 times out of 10, if I whap the STI hood fairly hard, the gear indicator gets knocked back to its proper place until I shift again, which makes me think it's a mechanical issue in the lever.

I'm thinking in terms of maybe a spring, or perhaps the piece that actuates the electronic signal to shift isn't returning properly after a real shift and is keeping the 'shift-to-a-smaller-rear-cog' signal always on. I don't have a schematic to look at, and haven't had the time to pull out my meter and trace out each conductor in the ribbon cable, but if no one comes up with a better suggestion, that'll be my next move when I have a hour or two.

I'm going to try cleaning the contacts and installing the 'standoff' pad behind the ribbon cable tonight, but was wondering if anyone else had had this problem, and if there is anything within the STI lever I might be able to look at and or lube to alleviate this. The levers themselves don't look too friendly in terms of taking apart and successfully reconstructing, so I'm only looking to the as a last resort.

Can anyone offer any hints on fixing this (and, no buying a Campy group and a Ergobrain isn't in the budget! :^))

Thanks!
-Mike
The cadence stays correct?...TFerguson
Jul 16, 2003 11:06 AM
Since the cadence is calculated from the gears its in, your problem has to be in the head unit. Send it to Shimano, they will replace it.

TF
Not totally clear, sorry.mleptuck
Jul 16, 2003 11:16 AM
The cadence is CALCULATED correctly (say, if I were really in 39x22 (if it existed in my bike), the display would say I was in 39x11 and pedaling at HALF the cadence I actually am). The actual arithmetic is correct, but the unit's idea of here my chain is on the back cluster is wrong.
I'm guessing that it is the connection...TFerguson
Jul 16, 2003 12:25 PM
I'm pretty sure that it reads the lowest cog when it is not connected at all. The two connections are:

At the shifter. Try the little spacer behind the connection. Also, when reconnecting, tighten the two little screws down each a little bit at a time. Watch the head unit to see when it starts working and stop tightening. It will quit when too tight as well as too loose.

Head unit into handle bar mount. Wiggle the head unit to see if this fixes it when you are having the problem. If it does, clean the contacts with an erraser and try again.

Mine also quits when it gets cold (or actually doesn't start till it warms up) but I doubt if that is any problem this time of year.

Hope this helps,
TF
Err.Dathon
Jul 16, 2003 11:19 AM
I have the same model Flitedeck and Ultegra. Some of the roads I ride are very rough, and a big bump sometimes gets it all confused. It will say that the cadence is 200, that sort of thing.

I found that removing the display part from the bike (it slides off the part that fits on the handlebar) and then putting it back on fixes the problem.

Now I wish someone could explain why I often get an average speed of Err.

Good luck.
Mine gives "ERR" for the Avg Speed about 1/10 times..TFerguson
Jul 16, 2003 12:15 PM
I can't find any consistancy to know what's wrong.
TF
More info!mleptuck
Jul 17, 2003 1:02 PM
Okay, last night I removed the head unit from the mounting bracket, cleaned all contacts with contact cleaner, cleaned the contacts on the switch and the ribbon cable in the STI lever, and installed the standoff pad behind the ribbon cable. On th work stand last night, it was working like a champ.

I took it out on a 60 mile ride today, and for the first 90 minutes, it was working like a champ. Then, I hit some crumby roads and the bumps set it off again.

I did, however, notice that if I just give a slight squeeze to the brake lever (just enough to tension the cable, not even enough to actually close the calipers on the wheel), the gear indicator would move to the correct position on the Flight Deck and stay there, until I shifted again (down or up, it doesn't matter in which direction I shift).

Now I'm REALLY suspicious of the STI level guts. I briefly read through the STI manual sheet last night, and thee was a mention of a lube point or two within the lever, so that's where I'm headed next, I suppose.

Does this additional info trigger any more suggestions from anyone?

Thanks in advance.
-Mike