Reconditioning STI System

[Jordan300]

A buddy of mine brought me his 2001 Trek 470 that he just bought and his front derailleur/derailer was stuck. The STI shifter would not release the cable to shift it down. At this point I realized I have no idea how to service these STI systems. PLEASE HELP>
Thanks Guys.

[cyclerUK]

I have had the same problem due to lack of use of the STI.
I just used WD40 squirted into the mechanism. Operated the STI a few times and it freed itself. I then re-lubed it with a thin oil.
It did it a couple of times but has now been O.K. for 12 months.
If you pull the STI brake back, you should see the little hole where the gear cable goes. That's where I injected the WD and oil.
I have never stripped an STI down so don't know if you can service them.
It may be worthwhile fitting a new cable inner to make sure it's not jamming, but you need to get the shifter in No. 1 position to remove the old cable.

[Jordan300]

Yeah that's my issue is that it is stuck in the number two position. The mechanism won't release to shift back down. I will try the WD-40 and I'll report back to see if that works.