https://community.usa.canon.com/t5/EOS-DSLR-Mirrorless-Cameras/EOS-1D-Mark-III-Err99/m-p/360917#M85164 <P>I have an EOS 1DMk3 that I purchased second hand many years ago.&nbsp; It will work fine for a while and then throw an Err99.&nbsp; I turn it on and off, I swap batteries, and still, it's Err99.&nbsp; So, I park it for like 6 months, put a newly charged battery in it and then it suddenly works.&nbsp; It will work perfectly for a while.&nbsp; &nbsp;Then it throws Err99 again, but if I keep trying to shoot eventually it starts working again for as long as I use it.&nbsp; When I turn it on again the process of Err99, continual shutter attempts makes it work again.&nbsp; I know the camera is no longer serviced, but I'd like to know if there is anything I'm missing that could make the camera a more reliable shooter?&nbsp; Regards, Tim Murphy&nbsp;&nbsp;</P> Wed, 26 Jan 2022 21:31:22 GMT jtmiv 2022-01-26T21:31:22Z https://community.usa.canon.com/t5/EOS-DSLR-Mirrorless-Cameras/EOS-1D-Mark-III-Err99/m-p/360917#M85164 <P>I have an EOS 1DMk3 that I purchased second hand many years ago.&nbsp; It will work fine for a while and then throw an Err99.&nbsp; I turn it on and off, I swap batteries, and still, it's Err99.&nbsp; So, I park it for like 6 months, put a newly charged battery in it and then it suddenly works.&nbsp; It will work perfectly for a while.&nbsp; &nbsp;Then it throws Err99 again, but if I keep trying to shoot eventually it starts working again for as long as I use it.&nbsp; When I turn it on again the process of Err99, continual shutter attempts makes it work again.&nbsp; I know the camera is no longer serviced, but I'd like to know if there is anything I'm missing that could make the camera a more reliable shooter?&nbsp; Regards, Tim Murphy&nbsp;&nbsp;</P> Wed, 26 Jan 2022 21:31:22 GMT https://community.usa.canon.com/t5/EOS-DSLR-Mirrorless-Cameras/EOS-1D-Mark-III-Err99/m-p/360917#M85164 jtmiv 2022-01-26T21:31:22Z