There is a way to turn off the a/c while the defog/defrost is on. When you push the def button, the a/c comes on automatically, but if you push the a/c button, you can turn the a/c off and the green light on the a/c button will go off, or the electronic display will show A/C off, and there you go, defrost/defog with no ac compressor. I have noticed though, that the a/c does help clear the fog from the windshield faster than with it off on a rainy day.