When I hit the auto button on my 2011 EX 4Cyl, the compressor seems to cut on, it could be around 50 degrees and it seems to cut on as well, since the engine seems to make some noise!!
It's normal. I think most cars us a/c way more than they need to. I don't know what the cut off is, but probably around 50F. My Honda does the same thing as did my Jeep Grand Cherokee. If outside is less than 70F, just push the a/c button, the light will come on, push again and a/c is disabled. It will not come on again until you push the a/c button or choose Auto. Note: if you start the car and it is warm out, it may select inside air, if so push the recirc button, it too will stay off until pushed again or you choose auto. Fan and mode will stay on auto. This is better than my Honda which never shows what it is doing unless you disable every function manually. Hope this helps.