Help! Canon 5D Mark iii - Autofocus issue - Works in live view and video but not through viewfinder

[Mandeep]

Hello fellow Canon users, 

I need your help! I haven't used my Canon 5D mark iii in around a month (Everything was working fine). Today, I turned the camera on to take some photos and to my surprise the autofocus doesn’t work. Below are the symptoms and also the things I’ve tried. After 5 hours of Googling I've exhausted all my options. I wondered if anyone out there may be able to help me. 

1) The autofocus works (As in the lens starts working) fine when in Liveview or in Video mode. 

2) The lens is 100% set to AF and not MF. 

3) When in live view and video mode both the half pressed shutter and the AF-ON button both work. Just NOT in normal mode (looking through the viewfinder and half pressing the shutter) 

4) I've check the custom button menu (C.Fn2) both the AF-ON and Shutter button are set to Metering and AF start.

5) The firmware is updated to 1.3.5

6) I've tried 5 of my lenses with the same result. 

7) When I look through the viewfinder I can hear the image stabilisation working and when I switch the stabilisation the noise stops

😎 I've tried all shooting modes A+, P, Tv, Av, M, B, C1, C2 etc

I'm completely lost and your need help. I've got everything crossed hoping someone out there might be able to solve this mystery. 

Thanks in advance guys! 

[Waddizzle]

Contact Canon Support to set up s service ticket.  I think they need to take a look at the camera.

[ebiggs1]

"Contact Canon Support to set up s service ticket.  I think they need to take a look at the camera."

Do that!

[jrhoffman75]

Since you say the camera was sitting idle for a month and just stopped focusing you could check one thing before you spring for service.

Remove lens and initiate manual sensor cleaning. Carefully, using a squeeze blower, blow off the AF lens at the bottom of the mirror box.

If a piece of mirror box dust settled on the lens it would affect AF. Its a long shot, but its free to try.

That also assumes that, just because you weren't taking pictures, no one accidently dropped the camera when moving it. If so, foregt the above and just call service as Wadizzle recommended.