I have a 70D and a T2i, and none of them turn on an AF assist light when focusing. I also have a YN465 which has an AF assist led and it works perfectly in both cameras. I believe the camera would have a similar light (like happens in nikon) using the same bulb that blinks when shooting with the timer, but maybe I'm wrong. The camera menu mentions an "IR assist beam", and I don't know if this is it, but at least it doesn't light up.
I looked for any video showing this light turned on, but couldn't find it. Can anybody give me an idea? Hope I was clear. Thanks in advance.