EF 70-200mm f/2.8L IS III USM constant focus noise

[PhotoDad]

My r6ii with rf-ef adapter and 70-200 f2.8 iii lens is now making a constant noise that sounds like it's struggling to find the focus. I've never heard it before.  I have bbf set.  Even with lens set to manual focus, the focus motor seems to be running. 

[SignifDigits]

Thanks Demetrius!  I thought I had read in your KB that turning the autofocus switch "Off" on the lens overrode the camera AF settings.  I guess I misread and/or misunderstood.  Thanks for setting me straight.  I find it bizarre behavior but nobody ever asked me to design a camera 🙂

[deebatman316]

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@SignifDigits wrote:

Thanks @deebatman316 !  I thought I had read in your KB that turning the autofocus switch "Off" on the lens overrode the camera AF settings.  I guess I misread and/or misunderstood.  Thanks for setting me straight.  I find it bizarre behavior but nobody ever asked me to design a camera 🙂

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@SignifDigits setting the lens AF/MF does override the camera focus setting. The specific camera setting called Preview AF/ Continuous AF causes the lens to focus constantly. Even if the AF Start button isn't being pressed. This will also cause IS to be on constantly too so its recommended to set it to DISABLE. Older lenses were not designed for the AF & IS to be active all the time.

[PhotoDad]

Many thanks to all of these suggestions. The fact that it happened when I've had the lens for 2 years and the camera for 1 and don't typically change the preview af/continuous AF option AND that it occurred on the xti I pulled out of the closet made me think this was a lens issue. I ran through your suggestions and found that I had preview AF disabled; I had Lens drive when AF impossible enabled (but no change when I disabled it); turning off image stabilization on the lens solved the problem. So this raises the next question: if it has never generated this noise before (I've never not shot without IS) is it time to get it serviced? It sounds almost like the motors are ginding a bit as I feel the body vibrating.