Fukishima could have used some of the trouble shooters on here. Way less explosions and radiation leaks would've happen.

Yes silly me warprints, of course you're right, the other option is to try the suspected faulty TC on another lens and see if you still have problems. Hopefully a store near you hawkdl2 will have one or the other in stock?

+1 what SkintBrit says. If all works well, except for when you add the 1.4 TC, then most likely it's the TC. Check the contacts on the TC. Is it possible to try the TC on another compatible lens?

hawkdl2 said:
The lens works perfectly without a TC as well as with the 1.7 TC. It's only with the 1.4 that is won't focus between 70mm and 100mm.

Putting my Sherlock Holmes hat on for a moment dear Watson............If that statement is correct, then I deduce that the problem MUST be with the TC14. Have you got a friendly local camera store that will let you try another one to confirm my suspicions? Remember, when you have eliminated the probable, whatever remains, however unlikely, must be the problem (truth)! Seriously, try and get hold of another TC14 and I think you'll have you're answer. Good luck.

Thanks very much for the comment and I will check for screws and contacts. but...

The lens works perfectly without a TC as well as with the 1.7 TC. It's only with the 1.4 that is won't focus between 70mm and 100mm.

However, to be clear, the lens DOES focus with the 1.4 TC at close ranges at all focal lengths, it's at mid to long ranges (over 50m or so) that it will not focus.

This sounds like something has come apart internally in the lens itself. Especially if the lens worked in the past. Something that occurs manually means mechanical. However, make certain all the electrical contacts are clean by carefully cleaning with contact cleaner, check for any loose or missing screws in the mounting area of the lens. If no one here has experienced this before, the lens may have to go to NIKON.

The problem occurs at any distance and at any light level between 70 and ~100mm with the TCE14II either manually or with AF. It works fine between 100 and 200, at appropriate distances - manually or AF.

No.

Sorry but don't know why. Are you focusing on something too close or too dim?

On my d300s, my 70-200 and 1.7 TC-EII focus fine at both limits of the zoom. However, with the 1.4 TC-EII the lens will not focus between ~70mm to 100mm by either manual or AF. I can hear the AF mechanism try, but it feels and sounds like it hits a limiter inside the lens. Is this normal?