35L AF hunting at infinity

Took the 35L walkabout with me today, and noticed an issue when focusing on anything more than 3m/10ft - the AF will often machine gun (rat-a-tat-tat) bouncing between 3m and beyond infinity, eventually settling at (around) 3m or beyond infinity. Any ideas of what might be wrong? I've tried remounting the lens, turning the camera off and on, etc and the contacts look clean, but I have yet to clean them to ensure that they are. Focus inside of 3m/10ft is the usual fast and accurate.

Thanks in advance.

Tested my other lenses this morning, and none are showing the same symptoms... maybe it's just time to send it in...

How many AF points active?

Single - center. With or without assist points activated.

WhyFi wrote in post #8110512
Took the 35L walkabout with me today, and noticed an issue when focusing on anything more than 3m/10ft - the AF will often machine gun (rat-a-tat-tat) bouncing between 3m and beyond infinity, eventually settling at (around) 3m or beyond infinity. Any ideas of what might be wrong? I've tried remounting the lens, turning the camera off and on, etc and the contacts look clean, but I have yet to clean them to ensure that they are. Focus inside of 3m/10ft is the usual fast and accurate.

Thanks in advance.

Hi there...I am having the exact same problem as you describe above with my Canon EF-S 17-55mm f2.8 IS. I know you posted this some time ago, but did you ever find out what the problem was? THANKS!