Shimano D/A shifter problem

OldGoat said:

Suddenly yesterday, my right shifter, which has been functioning fine since purchased, stopped shifting "down" from big to small chainring. After some experimentation, I discovered that if I hold the outer lever in its normal position with one hand while depressing the inner lever with the other, the shifter will shift. However, if I allow the outer lever to move slightly (as is normal) when pressing on the inner lever, the inner lever becomes stuck and will not move.

Shifter is 9-speed, flight deck compatible. I have disassembled the shifter per Shimano instructions (up to the point where Shimano says "don't go past this point or you won't get it back together again" in an effort to identify cause of problem. Nothing found. Reassembled shifter last night. Problem persists.

The flight deck cable is not a factor causing the problem. The problem is somewhere inside the forward metal housing. Cable tension is not an issue either, as the shifter is off the bike and has no cables connected to it at this time. If I hold the back (black plastic) end motionless, the inner lever will not move unless I also hold the outer lever motionless. If the outer lever is permitted to move when pressing on the inner lever, the inner lever will not move.

Ideas (other than "replace the shifter"😉?

Squirt a little Triflow into the works to see if that will free it up.
Take a close look at the insides to make sure no foreign matter (like a broken cable strand) is stuck in there.

Sometimes things just wear out and need replacing.

Yojimbo_ said:

Sometimes things just wear out and need replacing.

This sounds like the most logical way to look at the situation. 9 speed dura ace isn't exactly new, how many miles do you have on it and how long have you had it?

P.S. older shifters sometimes get gunked up inside just from years of dust, dirt, and sweat working into them. This can happen quite suddenly, too, and may be the cause of your problem. If this is the case, triflow won't do a whole lot just squirting it in there. Get a can of White Lightning Clean Streak and really soak the inside of the lever with it, let it drip dry. Then soak again and blow dry with an air compressor. Finally put a squirt of triflow in there and see if it works.

Yojimbo_ said:

Sometimes things just wear out and need replacing.

Shifter was brand new "old stock" bought two months ago from Ital-Tecno, so excess wear can be ruled out as the cause. Any other suggestions? Weird thing was that it worked fine at the end of the previous day's ride, and then didn't work the next morning..

OldGoat said:

Suddenly yesterday, my right shifter, which has been functioning fine since purchased, stopped shifting "down" from big to small chainring.

...

Okay, I presume you actually meant your LEFT shifter ...

Regardless (this is a serious question), were you wearing long-fingered GLOVES before this initially occurred?!?