Rebel T2i Autofocus freaking out

I'm sure someone has already asked this before, but I'm desperate by now. Just landed back in England for some travel and my camera has started acting up for the first time ever. I've got a Canon Rebel T2i, with the 18-55mm lens kit. It's been fine up until two days ago. The autofocus is just going nuts. It's trying to focus, but it just wont. It just keeps twitching back and forth like it's freaking out. Some of the time it will catch, and focus and take the shot. Manual focus seems to be working just fine though. Immediately after turning on the camera, autofocus will work, but not for long.
I've looked it up a bit, most people saying it's the focus ring, but mine doesn't seem to be stuck at all. The lens is attached properly, the contacts between lens and camera are clean and my firmware is up to date. The battery wasn't dead, but I charged it up thinking maybe that could be it, but it's just as bad as before.
I went into a camera shop in Oxford and all I got was "Yeah, it could be any number of things." Very helpful.
Anyone have any suggestions? I can't exactly send it in just now, I've only just got here, wont be home for over a month and would prefer a working autofocus!

Do you have access to another lens you can try?

Don't fault the person for saying that as they are correct.

I assume that you are shooting in a decent light level, not inside some poorly lit building where contrast (nneded for focusing) might be minimal. Remove any filters you might be using then like Christina has suggested, try a different lens; maybe a local shop that sells used equipment. Go in and try out some lenses under the guise you are possibly buying. If it still seems like the camera, ask around for a camera shop that does repairs.

You might also check the custom function settings, go here http://support-ph.canon-asia.com …nts/PH/EN/82007​50300.html.

To which AF mode is the camera set?...One Shot, AI Servo, or AI Focus...Try One Shot if you are in any other mode.

Tried all the AF modes, same thing for each. Freaks out the least in AI Servo, but I suppose that's only because I can still take the shot, even if it's not completely focused. Don't have another lens with me, but will try to stop into a camera shop today and try one out. Thanks for such quick advice.

Also, tried changing the custom settings, it was set on 0: AF/AE lock, and that seems to be the one is "works" best on.

I've had this camera since November and never had a single problem. Sunday night it worked, Monday it didn't.

More likely a lens problem than the body. If so, you have a perfect excuse to buy new glass.

Which auto-focus point(s) do you use? Is the camera set to a single AF point? If yes, do you see any dirt or debris covering that point when looking through the viewfinder?

I'd really rather have a lens that just worked! But I'm hoping it's more a lens than body issue.
The camera is set to a single AF point, I've not really changed too many settings and even reset them as some people have suggested. I've also completing cleaned the lens to make sure nothing was setting it off.
Wasn't able to get my hands on a different lens to try today, but hoping tomorrow will be more fruitful.

Try cleaning the lens to camera contacts.... both on the back of the lens and just inside the front of the camera.

Use a few drops of isopropyl alcohol (plain old "rubbing alcohol") to dampen a clean cloth and wipe the contacts with that. That will remove any oils, such as finger oils, from those contacts. Be careful to not touch the mirror in the camera or the optics of the lens. And, while cleaning the contacts in the camera, note that they are spring loaded pins and check that none of them is stuck pressed in. Sometimes that happens when a speck of dirt gets in there.

If you don't have, can't find isopropyl alcohol, those pre-moistened wipes used to clean computer keyboards and monitor screens can serve in a pinch, so long as they aren't to wet. Don't rub too hard with them either, they can be rather coarse paper and those contacts are gold plated.

Hopefully that will work. If not, well the best thing would be to test with another lens. Maybe a shop that sells Canon gear would let you borrow a lens for the test. If the borrowed lens works fine, you know it's your lens at fault. If the borrowed lens also won't focus, then it's a pretty good bet it's a problem with the camera.

Did your gear get knocked around at all while traveling? If so, could be a fault with either the lens or the camera. Usually I'd suspect the lens first, but it really can be either. That would mean a repair or replacement, unfortunately.

I hope a cleaning is all that's needed.

is it doing it in all modes? (action, Green Box, manual, Av, Tv, etc)

Try setting the AF to several different points and see if the problem continues. If you are able to identify that focus "hunting" only occurs when using a certain AF point, then chances are, there is some debris on your focus screen, impeding the AF from working properly when using a focus point that has some debris on top of, or touching up against it.

Look very closely in your viewfinder at a bright white object. If any debris is on or butted up against an AF "dot" then that point will not work.

Remove the focus screen. blow it off with a blower and you'll be fine. DO NOT TOUCH THE FOCUS SCREEN WITH YOUR FINGERS OR BLOW ON IT WITH YOUR MOUTH. (you'll get permanent fingerprints or saliva stains on it)

This happens with my 50D from time to time.

The AF sensor of Canon bodies is in the bottom of the mirror box, there might be some fluff or dust obscuring it. Also excessive dust on the main mirror might affect the light being reflected to this area by the AF sub mirror and may need to be cleaned

refer to figure 2 and 3 in this link

http://www.lensrentals​.com …how-autofocus-often-works

PUREBRAD wrote in post #14987772
Try setting the AF to several different points and see if the problem continues. If you are able to identify that focus "hunting" only occurs when using a certain AF point, then chances are, there is some debris on your focus screen, impeding the AF from working properly when using a focus point that has some debris on top of, or touching up against it.

Look very closely in your viewfinder at a bright white object. If any debris is on or butted up against an AF "dot" then that point will not work.

Remove the focus screen. blow it off with a blower and you'll be fine. DO NOT TOUCH THE FOCUS SCREEN WITH YOUR FINGERS OR BLOW ON IT WITH YOUR MOUTH. (you'll get permanent fingerprints or saliva stains on it)

This happens with my 50D from time to time.

Dirt or debris on the focus screen will have no effect on the performance of the AF system. The focus screen is located in the top of the mirror box while the AF sensor is in the bottom. Dirt or debris on the screen only affects what you see through the viewfinder, not what the AF sensor 'sees' and not what the image sensor 'sees'.