Tiagra 4700 left shifter problem

[goody]

Fitted a new tiagra 4700 groupset two weeks ago. well impressed after the old Campag Veloce that was on there. Shifting very light, smooth and precise. 400k later the front shifter is sticking.Starting on the front big chainring it is fine shifting down to the small chainring but operating the (brake) lever to shift back to the big chainring there is no resistance the lever moves in the full way but it's like it's not connected to anything.
Then if I flick the brake lever gently a few times it will start to work.
My thoughts are that it is something not returning to its position after the shift to the smaller chainring possibly cause by the grease used in its assembly and the cold temperature (it is cold today but not that cold?)
My initial feeling is to get it on the stand and give the shifter a good squirt of lubricant (WD40 or GT85)
I use the bike to get to work and returning the shifter (wiggle) would be a bit of a hassle. Anyone heard of this problem before and a solution?

 

[Ajax Bay]

First action is regular repeated squirts of GT85 (as you've said you're going to; doesn't need to be on a stand) and see how it goes. Sorted mine RH STI (Tiagra) with these symptoms. Gets a squirt every clean now. Did find that applying the brake slightly (but not as far as the blocks touching the rims) meant the STI would then work. Also I threatened the STIs with replacement: they started shifting.

 

[Stumac72]

I've had the exact same thing happen today, first time I've had to use the small chainring on my 4 week old Cannondale. The first two times the lever started working again after a few minutes, on the third occasion it didn't. 9 hours later and several liberal squirts of WD40 and it's still not working. I'll be asking in the shop tomorrow.

 

[Ajax Bay]

I'll be asking in the shop tomorrow.

Share what their judgement is, and how they resolved it, please.

 

[Stumac72]

Just to update, the shifter started working again 15 minutes into this morning's commute. I'll post any info I get from the shop later.

 

[goody]

Mine have gone back to wiggle.

 

[Stumac72]

I explained the problem to the guy in the shop. He said he didn't think it was grease causing it but didn't know what was. I'll have to take it in at some point.

 

[goody]

Whatever it is it shouldn't be happening.