Auto focus problem on a Canon 70-200 F4 L USM lens

[jonnybantom]

EF 70-200mm f/4.0L USM
Summary: Hello, can you help me please, the above lens will not auto focus properly. If i manually focus the lens and then switch to AF it will slowly auto focus by continually pressing the camera auto focus button on and off. I can not get it to focus in any other way. My other lens's are fine on the camera so it must be a fault on the lens. Any idea's as to anything simple to check as Canon require £220 just to look at it.

 

[vetonbike]

Hi the Jon by the camera auto focus. Do you mean the shutter release button. And have you tried giving the lens contacts a good clean.

 

[jonnybantom]

Hi, thank you for the reply, yes i mean the shutter release button and i have cleaned the contacts

 

[Carlo]

Do you have a filter on it?
I'm sure i've read of some problems with this lens having autofocus problems when fitted with certain UV filters!

 

[vetonbike]

Then as you say it is probably an internal wiring fault.

 

[jonnybantom]

Even with the filter removed i still have the problem. It was fine one day and faulty the next

 

[dave_bass5]

There is a known fault with some of the later versions of this lens. IIR it manifested itself if you point the lens up and use AF or something like that to infinity. (sorry, ive never had this issue but a mate did, but i never really paid attention to what the cause was)