There are a few other threads I recall on this too. Let's suffice to say the heat & A/C controls on this car (and my Murano for that matter) are a fail by Nissan.
Someone else speculated that the A/C comes on with recirc to avoid fogging up the windows in such a small cabin. This doesn't explain the Murano though.
I too have learned to live with it and pretty much have to push the A/C off with every change to the controls.
