I had a 1992 Maxima in the US. The car had automatic climate control. The AC button had to be depressed if you wanted the system to use the AC to meet the desired temperature.
If you wanted to forbid the system from using the airconditioner, you had to press the ECON button.
Of course, if it were too hit outstide, the system would fail to meet the desired temperature while the ECON button was pressed.