Canon 40D Auto Focus Appears to be Broken

Hey everyone,

I'm new to the forum. Yesterday, the auto focus on my 40D stopped working. When the AF switch on my lens is on it won't take a picture. It also won't focus or allow you to select a focus point. Also when in AF all my controls are disabled, can't adjust shutter speed, f-stop, etc... The scroll wheels don't work. I get different results in different creative zones. Some will not let me shoot in AF or MF, others only allow my to shoot in MF. But none work in AF.

If I switch it to MF on my lens everything seems to be fine and I can shoot. I switch from AF to MF pretty often using the switch on my lens. Tried a different lens and I'm still having the problem.

I also noticed before this happened my camera has been having a difficult time focusing in AF mode.

I was out shooting yesterday in the city where it was very cold. I didn't have my camera out for extended periods of time though. I only pulled it out from time to time. Not sure if that could have something to do with it.

Has anyone had similar problems? I really hope it's not broken, I shoot daily and have been loving my 40D until this happened. Any help would be greatly appreciated. Thanks in advance!

I've not heard of that particular focus problem with a 40D or any camera for that matter. Have you tried the eraser trick on the pins in the camera in case there is a problem with the contacts? Since it happens on more than one lens the problem is obviously the body; if using an eraser to clean the body's electrical contacts (hold the body up so the eraser bits fall on the ground, NOT INSIDE) doesn't work then unfortunately it probably needs to be repaired.

I shoot in the cold all the time with mine, no problems so far shooting birds and stuff in -10 to -20C. I don't use manual focus very often (I switched to EOS to have autofocus) but I do flip the switch occasionally on my lenses without problems.

I don't see how the lens could possibly be affecting all the operations on your camera. Even with the lens off, you would be able to select AF points, and the scroll wheel will still change EC or shutter speeds, etc.

What mode do you have the camera in when you cannot set the AF point? I also have never heard of this issue before. If you cannot figure it out, most likely you will have to schedule a little vacaction for the 40D in CanonLand.

Yeah, I just tried my 40D and I can select AF points fine with the lens off. Only the Auto modes prevent me from selecting AF points (yikes, I had to move past P...). I can't see any custom functions which would do this either. Sounds like a Canon spa vacation for your 40D sadly unless someone else has ideas.

I couldn't see where you said this happens with all your lenses. Do you have only one lens?

Before sending the body in for a spa retreat, I'd consider trying another lens. (obviously - unless you have and I just don't see where you said you did).

hpulley wrote in post #9503346
Have you tried the eraser trick on the pins in the camera in case there is a problem with the contacts?

Just tried this, it did not fix the problem.

TeamSpeed wrote in post #9503348
What mode do you have the camera in when you cannot set the AF point?

To clarify, I can select the AF point in all the manual zones. But when you push the button 1/2 way in any zone the AF points don't come up or beep.

RandyS wrote in post #9503545
I couldn't see where you said this happens with all your lenses. Do you have only one lens?

I tried a different lens, same problem occurs.

Also, I it seems to be not working in full auto mode at all now, either in AF or MF.

Should I try to reset the camera to factory settings?

Worth a shot to reset it and try that. Otherwise you'll have to take it back to the store or send it to Canon for repair I'm afraid.

Remove both batteries then try again.

Have you been screwing around in the menus? Did you somehow enable the "back button" for focus? You need to reset the camera to factory defaults and start over.

Will the shutter fire in AI servo?

justin.lancaster wrote in post #9504270
Just tried this, it did not fix the problem.

To clarify, I can select the AF point in all the manual zones. But when you push the button 1/2 way in any zone the AF points don't come up or beep.

I tried a different lens, same problem occurs.

Also, I it seems to be not working in full auto mode at all now, either in AF or MF.

Should I try to reset the camera to factory settings?

Do you have AI Servo turned on for your focusing mode? The points won't light up in AI Servo. I agree with the others, 1) use the menu to reset all CF functions, 2) use the menu to reset camera settings, 3) take out the main battery and the small clock battery if you can find it, and let it all sit for 30 minutes. Pop everything back in and try again. I think you have set some settings or CFs that is causing your 40Ds unexpected behavior. If resetting works, I would suggest going through the manual again to read about the different settings.

440roadrunner wrote in post #9504444
Have you been screwing around in the menus? Did you somehow enable the "back button" for focus? You need to reset the camera to factory defaults and start over.

Will the shutter fire in AI servo?

Reset camera settinga and custom settings... No luck.

The shutter will not fire in AI servo unless in MF mode.

Also, I've noticed after turning the camera on and off an putting it back in AF mode it still won't focus but when I push the shutter 1/2 way it flashes busy for a few secs and then the viewfinder screen shuts off and nothing works. It strays this way until i turn it on/off again.

Just popped the batteries out will try again in 30 mins.

Justin said it doesn't work in full auto mode either so that tells me it isn't a setting or the back focus button as full auto mode ignores all your settings.

If the batteries out reset doesn't work then I'm afraid it sounds like repair time unless someone near you can handle it and check it in person.

YES!!!!!!

Battery removal fixed the problem! It is working fine now, AF and MF works in all modes!

Phew. Glad I didn't send it back to Canon for them to do that. Probably would've cost a pretty penny.

Can anyne explain why that would happen? Or what the battery removal reset does?

Thank you all so much for your help on this!!

justin.lancaster wrote in post #9508015
YES!!!!!!

Battery removal fixed the problem! It is working fine now, AF and MF works in all modes!

Phew. Glad I didn't send it back to Canon for them to do that. Probably would've cost a pretty penny.

Can anyne explain why that would happen? Or what the battery removal reset does?

Thank you all so much for your help on this!!

It clears the menu setting memory, so all button functions are reset to factory default. Chances are you might have missed something when manually resetting the custom functions.

I've been working with computers from big mainframes to those little apple things for over 40 years. Whatever goes wrong, before you do anything else, switch off, physically disconnect from energy supply, reconnect after 1 minute, switch on and try again. If all else fails, a thump in the bottom right hand corner is a useful Plan B.