Canon 17-85 f/4-5.6 IS USM focus hunting DIY fix

[rutteger]

The internet is awash with guides for repairing this particular Canon lens but the main focus is on the ribbon cable which seems to fail. Had this fix completed by canon 3 years ago under their fixed price scheme which was at the time a fair £52.

Now the lens struggles / refuses to focus - it hunts back and forth before finally focusing, often incorrectly. If one uses manual focus everything works fine, i.e. focus on the subject which the camera then indicates is in focus via the viewfinder. The aperture still works ok, no errors on the body. Other lenses work fine, have cleaned contacts etc. etc. Canon now was £78 for a fixed price repair.

Chances are I'll get back what I can on the 'bay. However wondered if anyone had experience of cleaning the AF sensor in the lens, have read this as a possible cause of this issue. Struggling to find any decent guides for this fix. The other possibility which has been suggested is a duff lens motor which would render a repair uneconomical.

 

[Wozzaaah]

I have one that does exactly the same even after I dropped a complete new aperture unit into it.
It sometimes focuses fine but sometimes hunts and when it thinks it's got focus it often hasn't.
It's the body that decides when focus is achieved not the lens so there's nothing inside the lens to clean to fix the issue..
Mine will be heading off to the Bay of E as spares or repairs too as it's just not worth spending money on.

 

[rutteger]

Forgot about this thread. On balance and having read various forums posts etc elsewhere the lens ended up on the 'bay.