Automatic focus not working

Are you pressing the shutter button half-way to allow the camera to lock in the focus before pressing the rest of the way?

Does this problem still exist when you have the shutter pressed halfway down?

Regards,
Worldvet

The letters you're referencing is the M/A (manual / auto) focus switch. The lens has this switch and operates in Auto Focus mode when set to "A" and manual focus mode when set to "M".

You have to manually focus on the subject when in letter "M". If you do not, the result will be out of focus. From your description, it sounds like the camera / lens combination is attempting to focus and operate the shutter in auto, and focusing in manual; but due to some type of damage resulting from possible mishandling, exposure to dust, dirt or even moisture is interfering with the successful completion of the process.

You could isolate the problem to determine if the cause is in the lens or camera by simply attaching the lens to another compatible Nikon camera or placing a different auto-focus lens on your D40. The problem will either stay with your D40 or follow the lens when attached to a different camera. It is also *possible* that due to numerous attempts of auto-focusing with your D40 & lens combination, that both the lens *and* the camera have been damaged. If the problem is severe enough, the problem in the failed device could cause failure in the otherwise normally working device, too.

You might be best served by contacting Nikon Service & Support below:

http://www.nikonusa.com/Service-And-Support/Service-And-Repair.page

You also said you lost your manual. You can download the manual for the D40 directly from Nikon in your choice of English, French or Spanish from the link below:

http://support.nikontech.com/app/answers/detail/a_id/14157/session/L3NpZC9YRTgxQVpKag%3D%3D/kw/D40%20manual/p/19%2C334/c/187/r_id/116678/sno/0

Good luck!

Hi Needs a new HMS motor

THERE is a problem in lens not with the UV filter
remove the lens clean the contact of lens & camera if not working repair or replace it

I have similar problem on my D40. I think there is something mechanical with the camera's shutter button, some connections, I guess... The only solution I've found is to go to Menu > Custom Settings Menu > "AE-L/AF-L" and set to "AF". Now you can focus by AF-L button. Focusing works then perfectly. The WORST thing is that I can't lock exposure now and that's sad :( Maybe I can try to fix this in the camera center later, we'll see. But it takes months in Ukraine to do the fixing... Hate that!

has the lens stuck up? put it temporarily on 'M" and try to turn the focus ring. this should be freely turning;

otherwise you may want to check the camera body to lens electrical contacts (silver).. a small dab of alcohol to a q-tip.. make sure its not that wet..then try to clean the contacts.

I assume the lens had the impact. The 18-55 lens has the built-in motors for auto-focus.
Try switching to manual focus (on the lens). If this works, the lens may not auto-focus anymore.
Try it and let me know.
cheers,

When the camera is in auto focus mode, it will not take the picture until it locks onto a subject. If there is not enough light, the camera will "hunt" for something to focus on. Since it can't define any edges, it won't allow the shutter to release.

The D40 base model does NOT have a powered focus lever for autofocus, so if the autofocus is not working, suspect the lens.

I fixed it!! Turn the lens to Manual mode (moving to M). Twist the very tip of the lens till it unlocks.

If you twist the lens on the end far enough on the end to the right you will find it "locks". This is what is causing the screeching sound,, it's locked and can't auto focus. Twist the very end to the left till it releases. This fixed it for me.