I am also having the same issue all of a sudden. On the last two outings, I had to dismount and remount the lens to get AF to return. On the last, I also got a very loud metallic click a few times, when pressing the shutter. I was using burst mode and when it happens, everything freezes until I release the shutter button. This is the same sequence had with my G1, which was finally replaced after 3 attempted fixes. I haven't had time to do much shooting lately so am muddling through, but when I finally get home it is going back to Tamron.
I mailed it off to Tamron repair today. The local rep offered to let me use his copy of the lens while mine was out for repair. A very nice offer, but I didn't want to be worried about damaging someone else's lens if I fell or dropped it or something. I've never damaged a lens or camera in an accident in 50+ years, but it would be my luck that this would happen when using someone else's lens.
Anyway, Tamron support continues to be excellent. I just wish the lens would work for more than a couple of weeks after repair.
Woody,
To me it seems to be an intermittent problem that maybe when they "bench test it" does not show up. Back in the 70's I had a Zenith Color TV bought new shortly there after during a few month it would periodically cast a blue haze on the screen then disappear. Oh this was the time the tech would come to the home but we could never replicate it finally after two "house calls" I told them to take the TV (it was one in a real wood cabinet) leave it running at the shop (this was before the big box stores). A couple of days later they called saying they saw the blue haze and were able to locate what was wrong and replaced the defective part.
Probably when the fellow said he let you use his lens it might have been better to have the tech use your lens in a real world environment so that he/she would see it act up.
Hope it turns out okay.
Lou Cioccio
Well, when I got the Tammy 150-600 back, I had the same issues. Still refusing to focus, locking up at infinity or minimum, and the aperture sometimes staying wide open when set for smaller. I threw in the towel, and bought the Nikon 200-500. After three outings with the Nikon I can tell you it's sharper, the VR is better, and I'm getting a higher hit rate on difficult shots like birds in flight. And, NO problems with refusal to focus.
Now what to do with and about the Tamron 150-600? I'd like to sell and make back a chunk of the money I spent on the Nikon, but I will not sell a lens that is not functioning correctly. I suppose a call to Tamron is in order to talk to someone high on the food chain.
It is really disappointing to me since every other Tamron lens that I've ever had has been great.