Canon 40D Auto Focus Appears to be Broken

Hello all,
Just wanted to tell you that I had the exact same problem with my 40D, so I followed your advice about the batteries and it's all fixed! Thanks so much.
Kate

drkate wrote in post #9553575
Hello all,
Just wanted to tell you that I had the exact same problem with my 40D, so I followed your advice about the batteries and it's all fixed! Thanks so much.
Kate

Ok, I have this problem right now. The camera will not focus (no matter whether I have it set at P, Tv, Av or whatever). The really weird thing is that I have tried my 24-70, 100-400, 10-22 and 50 1.8 to see if it was an isolated problem and found that the only lens that works properly is the 10-22! What the heck?! It's the only EF-S lens I checked. I wonder if that really has anything to do with it???
I've got the batteries out of it right now so I'll let you know what happens.
Thanks

OK, I tried the thing with the batteries and still nothing. I've cleaned this and that and, so far, to no avail. Any other ideas out there?
Thanks

I had the exact same problem with my 40D. I was using non Cannon batteries, could that be a contributor? Had shot with those batteries many times before though. Anyway pulled the batteries out, put my Canon batteries in and it cured it. Makes me nervous for the future though. better buy a backup. Thanks for all the info..
-Pat

Yep. I've noticed that when a non-Canon battery starts to go it goes quickly (although it can still show at least half charged on the LCD) and all sorts of weird and wonderful things can happen.

jim.holder wrote in post #10372950
Yep. I've noticed that when a non-Canon battery starts to go it goes quickly (although it can still show at least half charged on the LCD) and all sorts of weird and wonderful things can happen.

I find nothing strange happening with my non-canon batteries (LP-E5)

drkate wrote in post #9553575
Hello all,
Just wanted to tell you that I had the exact same problem with my 40D, so I followed your advice about the batteries and it's all fixed! Thanks so much.
Kate

ditto here, took the battery out, put it back in and everything is fine. Thanks!

I seem to be having a similar issue with my 40D. I have the canon 28mm f/1.8 prime (brand new) and the canon 60mm macro. When I put the 28mm on it works perfectly if I use it in a landscape (upright) position, but if I turn it on its side (portrait) and/or point the camera in a upward direction I cannot auto focus or take any pictures. If I move the camera around in different positions and keep trying occasionally it will focus and allow me to take a picture. If I put the camera back upright it works perfectly.

Now, if I put my 60mm on it works flawlessy no matter what position i put it in. I then put the 28mm back on and it acts up again. I then had my friend put the 28mm on his Mark II and it worked perfectly. In fact it worked so well he is thinking of getting one.

I have pulled the batteries (canon) and that did not help. I did not try the eraser trick because it works perfectly with my other lens. I have not cleared the camera yet. I guess that is my next step.

This is so strange how it works perfectly as long as I don't tilt the camera. Has anyone heard of this before? Any ideas?

Keep in mind the 40D shutter button has been known to fail prematurely... I believe there are fixes out there on the interwebs.

http://www.google.com …40d+shutter+but​ton+repair

That is good information. Thanks.

I am thinking it must be a contact issue since the lens can be put on another camera and work perfectly. Plus the issue only happens with this lens on my camera, no others. I plan to do some detailed troubleshooting tonight with all the info I have read in this forum and see if I can narrow it down some more.

BTW...I am note4shawn (old login)

I know this thread is older, but it came up on google when I was searching for answers for the same issues as the OP. My camera doing exactly the same things. In case this helps anyone else, I just want to confirm that the suggestion for removing the battery of 40D was also the solution in my case. I was so pleased to have it resolved I just had to sign up and thank the wonderbods here who suggested it.
thank you
Metta

Did you remove just the primary battery (BP-511A) or also the clock battery?

I believe you remove both batteries so the camera can reset itself to all factory default settings.

But it doesn't just because you remove the batteries. It does a restart of the CPU, yes, but the settings are stored in flash memory, so they are non-volatile and will remain during battery our. The backup battery is there to keep the clock running, nothing else.