EF100-400mm L IS II USM suddenly stopped focussing

[MikeMazet]

I replaced my EF100-400mm first series lens with 2nd series a couple of years ago. I noticed over the last few weeks that focussing had become problematic with the lens failing to focus on the occasional subject (mostly birds among thickets of tangled branches). This seemed intermittent and I was hoping it was the branches that were causing the issue. But, suddenly, overnight the lens stopped focussing altogether, and that's when pointing at clearly defined, uncluttered subjects. I am an experienced photographer and know this isn't down to wrong settings etc. But what can be the cause? Are the motors on these lenses likely to fail after 2 years? The motor still drives the focussing but not every time, and it never achieves focus. After a couple of whirrs it gives up. If it's the motor, is it worth replacing? Anyone know the cost? (I'm in France, so a € price would help.)

[Waddizzle]

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@ebiggs1 wrote:

"Testing the lens in Green[A+] mode has the net result as resetting the camera."

I don't like the "Green Square" always telling people with this level of camera to forget it even exists. If you want a P&S buy a PowerShot. But if you are going to buy a semi-pro camera you should be beyond the Green Square! Besides I prefer to have the camera set back to a completely known zero in every respect.

Sorry it didn't work but now you know for sure. Call Canon 1 (800) 652-2666

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I am sorry the suggestion does not meet with your esteemed approval, Ernie.

It is called a test, Ernie.  No one is telling them to use that mode for shooting.  It is a simple test that simply bypasses any custom settings changes the user may have entered.  

I see no reason to tell someone to clear out their settings when one turn of the knob can do it without clearing the camera.  In fact, doing a factory reset does not fully reset the camera, anyway.

BTW, going into the menus to do a factory reset is too much of a deep dive for some folks.

[Anonymous]

I think that you've checked everything that can be tried to troubleshoot the issue. It is definitely worth getting that lens repaired, it is a great lens. Good luck.

[ebiggs1]

"I am sorry the suggestion does not meet with your esteemed approval, Ernie."

You seem to have problems with people that have a different opinion. I simply explained why I don't, yes ever, recommend using the Green Square. If you feel differently that's OK, you can tell folk to use it. 

"BTW, going into the menus to do a factory reset is too much of a deep dive for some folks."

Then this person truly needs to have bought a PowerShot and not a 5 series.