Misbehaving autofocus

[_rubinho_]

I have a Tamron 18-270mm PZD Nikon fit which I think has started to misbehave. The focus distance scale on the focus ring goes (m) 0.49, 1, 3, 7, ∞. Problem is whenever I autofocus on something more than 2-3m away it rattles right round to the ∞ stop. I've only just noticed it doing this but it may have been doing it for a while. Does it sound like I need to get it looked at?

Camera body is a D5100 and my other lenses (kit 18-55mm and 35mm prime) work fine. I've tried all of the different combinations of AF setting.

Any other ideas?

Edit: the Tamron has this behaviour through the zoom range.

[Ledaig]

You could try cleaning the contacts on both the camera and lens, it may be that a slightly dodgy connection is causing the problem.

[GravelBen]

_rubinho_ said:

Problem is whenever I autofocus on something more than 2-3m away it rattles right round to the ∞ stop.

Just to clarify - do you mean it focusses to infinity, or that it focusses where you want but the dial shows infinity?

[_rubinho_]

GravelBen said:

_rubinho_ said:

Problem is whenever I autofocus on something more than 2-3m away it rattles right round to the ∞ stop.

Just to clarify - do you mean it focusses to infinity, or that it focusses where you want but the dial shows infinity?

It focuses to infinity.