In my case, my 70D's AC continued to work, but was weak. So I am uncertain if this situation falls within the bound of what the OP and others above have posted.
Here's the situation.
We are having a weekend of what is (for us) an unusually hot spell of weather, with temperatures approaching 100F and high humidity. Unusual for the Boston area.
On Thursday and Friday, the AC seemed a bit noisier than usual as i was driving, and although the AC was working, I had a vague sense that something was not quite right. But my trips were not long enough to quite tell.
Yesterday morning, we had a trip to a social event about an hour away. I started the AC from my phone at about 10:30 AM. I noted that the initial cabin temp was 125F, probably the hottest I have ever seen it. The car was parked in an open parking lot, in the sun since shortly after sunrise. Ambient temps by then were around 90-92. My car has a sunroof, and I have no screens or special protection on the glass.
I had cabin overheat protection enabled, but it does not run after 12 hours since the last trip, so it did not actuate.
We got in the car to leave about 30 minutes later, and the cabin was not very cool. The phone app said it was about 80F in the car. The compressor was working very hard -- we could hear it from across the parking lot as we left our condo. It sounded normal, but if it was cooling something, it must have been mostly the battery that got the benefit.
We had a trip of about 1-1/4 hours. mostly highway. As we drove, the cabin temperature did not improve. I played with adjusting the controls to see if it would help -- I shut off air to the back seat, and manually cranked up the fan speed. Those steps helped a little initially, but the cabin seemed to get gradually warmer as we drove, not cooler. It was somewhat cooler than outside, but definitely uncomfortable. The ambient temp was about 95F by the time we got to our destination.
I was disappointed, to say the least. I don't recall ever experiencing such limited cooling before, and we have certainly driven in 90+ heat before.
When we returned home, it was early evening. The car had been in the shade for a while, and of course the sun was no longer as high in the sky. It was still 92F out. But the cabin was nice and comfortably cool on the return trip. (I used the AC for about 15 minutes before we left, and the cabin was already cooled down when we got in, as it should be.)
My theory -- the battery was overheated from sitting in the asphalt parking lot before we left in the morning and the AC was devoted mostly to keeping that cool. But if so, the AC system is either inadequate for 90+ temps on a sunny day, or my AC system is not working up to snuff.
I keep seeing posts from people who live in AZ that say their cars are fine in 110F+ heat, so maybe I should schedule an appointment to have the system checked. But unless the technician checks under similar conditions to yesterday, I am not sure they will see any problem.....