EOS 5D Mark III won't take photo, sometimes won't turn on at all

[NorthernAvocet]

I have a Canon EOS 5D MK III body which has an intermittent fault.

With the battery fully charged the camera is turned on and the LCD panel display screen is on but I am unable to release the shutter. The autofocus does not work when this fault is apparent. Often the camera will not turn on and there is no display on the LCD panel.

The menu screen display will not work when the menu bottom is pressed.

I have tried two different lenses, and the fault is the same.

The camera was purchased secondhand about 9 months ago in very good condition with a low shutter count

Any thoughts as to the cause of this fault?

[shadowsports]

Unfortunately, the 5D Mark III is no longer being serviced by Canon.  You might be able to find an independent repair shop, but tracking down a problem like this might be expensive.  The camera is approximately 13 years old.  Great in its day.  

Since the behavior is happening with more than one lens, You can try the following. 

Test with one or more Canon brand batteries.  Test with one or more CF Express cards of known quality and health. 

Reset the camera settings both main and custom, then retest without making changes.  

This should help you confirm the problem.,

Ultimately, my advice would be replacement as a repair could exceed the cost of a new or used body.  

[NorthernAvocet]

Hi Rick, it is definitely a fault with the body, fortunately I just got another body but would like to repair the older one. Canon Thailand (where I live) do still repair these models, so next time I go down to the big city I will take it there. Thanks for the reply.