Canon 100D won’t focus

[Cogitare]

I have probably changed a setting or so but I can’t figure this out. When the camera hasn’t been used for a couple of hours, I can only do about 1-2 autofocusing before the tracking zone on the screen becomes red. (The camera lens won’t move at all). The lens is a standard 18-55mm kit lens that was included in the box. I have tried all of the AF operations and none of them works. And yes, the lens is switched to AF.

I do rely on the auto focusing a lot so I would be really grateful if any of you had an idea of what may cause this issue.

[MikeSowsun]

The camera actually has two independent AF systems. One for Liveview and one for the optical viewfinder. 

Does the problem also happen when using the Auto Focus through the viewfinder?

If they are both giving not working properly I would assume it is the lens that is causing the problem, not the camera. 

If the optical viewfinder AF is okay, then you can eliminate the lens as a problem and concentrate trying to fix the Liveview AF. 

[Cogitare]

I just tested to use autofocus when using the viewfinder but neither did it work there. However, I discovered something weird when doing that. The very right autofocusing point was blinking red even though it clearly wasn't focused there. I tried to point that specific AF point to objects close and far away, but it always said it was in focus. The lens didn't rotate a single degree. Maybe there's something wrong with that AF point?

[John_]

Have you tried resetting your camera to its defaults thru the settings menu yet?

[Cogitare]

Yes, I did that a week ago. It didn't solve it 😞

[John_]

How do the contacts look on the lens and camera body? Damaged? Dirty? Also how old is your battery?

[ebiggs1]

Call the friendly folks at 1 (800) 652-2666

[Cogitare]

The contacts look all fine and I recently did a quick clean. The battery I’m using is the one that came included with the camera itself, so about two years old (December 2016).

[John_]

The least expensive option is to try a new Canon battery. Does it focus correctly when the battery is right out of the charger, fully charged? It may be not able to hold a charge for a reasonable period or for those times when it is just sitting idle and does not have the power to run the lens.

[Waddizzle · Accepted solution]

I suspect that the AF motors could be misaligned and jammed up.

https://community.usa.canon.com/t5/Lenses/Autofocus-not-working-18-55mm-lens/m-p/138114#M5459

That link describes a solution for the older EF-S 18-55mm lenses.  The older lenses do not have manual focus override.  It is all too easy to reach up to turn the zoom ring while looking through the viewfinder, but actually turn the focus ring, which can cause the AF motors to become jammed.  

The newer “STM” lenses do not suffer from this problem., because their focus rings have manual focus override.  One dead giveaway that this could be the issue with your lens is that if you detach the lens from the camera and shake it, you will probably hear a faint rattle.