Bicycle Mechanics - flight deck problem

Hi: I've been using a flight deck computer on my Ultegra 9 speed bike and it has always worked perfectly. I recently installed a unit on my daughter's 8 speed Sora bike and am having a problem with the left side contacts (I believe).

The computer works perfectly for every function except the gear indicator for the front chain rings (triple).

I have it programmed correctly for a triple, 8 speed. I've double checked.

The gear indicator display shows three positions for the front chain rings, but won't register the middle ring. The indicator display shows the large ring when the chain is on the middle or large ring. It shows the small ring when the chain is on the small ring. In other words, it doesn't "know" when the chain is on the middle ring and "thinks" it's on the large ring.

I've opened up the shifter/brake hood and removed the sensor piece. I've cleaned all of the contacts with electronic contact cleaner. I've tried more shims and less shims (which I have had to adjust on my other bike, so I know how to do it).

I've tried a different computer head that I know works, and have changed the battery. Same symptoms.

My conclusion is that there is a problem either in the contacts in the shifter itself, or in the corresponding contact that is wired to the computer. If it's the contacts on the wiring harness, that's a relatively easy fix. But if in the shifter itself, I'm wondering if there is a part that can be replaced or if I'm screwed.

Does anyone know how to trouble shoot this? I have a multimeter and know how to use it!

Thanks for any advise you can give.

It's been awhile since I've done any work on Flight Deck computers. I vaguely remember making a "spacer" from masking tape to put behind the contact ribbon in the shifter. The spacer pushes the contact tape against the wire harness and may solve your problem.

It's been awhile since I've done any work on Flight Deck computers. I vaguely remember making a "spacer" from masking tape to put behind the contact ribbon in the shifter. The spacer pushes the contact tape against the wire harness and may solve your problem.

Yea, that's what I was referring to when I said I'd tried more and less shimming. I don't think that's the problem. Thanks anyway.

After cleaning everything up a couple of times, messing with shims, etc. I finally just tried a new wiring harness and the thing works perfectly. Oh well, sometimes a new part is needed.

Have you found a solution to the problem that the buttons are too easy to press accidentally? I was forever accidentally stopping it by pressing the left button, which was really irritating. I was finally able to get a small O-ring and slip it around the button under the hood. That made it a bit harder to press the button in and seems to have fixed my "problem".

Just a tip in case you've had trouble with this.