Mainly I would like to know if anyone can tell me what my issue is known as and if anyone encountered it before... maybe can enlighten me on the cause too.
The lens is a Canon EF 24-85mm F3.5-4.5 USM. Recently, it has been on a hunting spree, even under bright sunlit conditions. While on other occasions, it seems fine. When I say 'hunting', it doesn't actually hunt the full cycle and not lock, rather, it hunts half cycles, and really rapidly. Looks like just "zooming" in and out.
It will go away after awhile and act like a normal lens, but once it misses focus again, it will start hunting and it hunts on every other object afterwards for awhile.
1) I understand how normal focusing works and I did target high-contrast areas to test, I am certain its an error and not normal hunting.
2) My other lenses work fine, so I guess its not the body, body is a 20D by the way.
3) I have cleaned all electronic contacts, doesn't seem to be the problem.
I bought it 2nd hand from TCW, they told me they'd give me 3 months shop-warranty, when they say that, do they usually fix the lens on their own or send it to Canon?
Thanks in advance!