First, ignition on, or best yet engine running.
Second - set the air flow to windshield only (it may increase air flow automatically, some cars do that, like Rondo)
a note - you not supposed to see A/C light to come on as of now; however, make sure A/C compressor kicked in
Third - push the recirculate button (that one that says closed air circulation) at least 5 times within three seconds. As a result the light should blink.
Logic is disabled.
However, keep in mind that it may not be completely disabled, meaning when you have air setting to the floor, and then switch to windshield, A/C will kick in itself, BUT you will see the A/C light coming on at the same time. You can MANUALLY turn it off.
In 2009 Elantra I disabled it as I described above (make sure you are using the button - closed circulation, not the from far right side - fresh air allowed in - IF this did not work, try the latter one).
However, I noticed that IF I live the FAN in OFF position when restarting the car, then when I turn it back on, the A/C does not kick in (regardless of air selector position).
This is what I do on my auto climate control (see bottom of post), so different setup, but maybe same procedure? maybe hitting the a/c button at the same time is the ticket...
On my car, all this does is make it so the a/c led lights up when the position is set to blow on the windshield (when logic is on the a/c goes on, but the light doesn't light up to tell you so). So the a/c still turns on but at least the system tells you that the a/c is on, so you can turn it off if you like. It doesn't actually prevent the a/c from coming on when the air is blowing on the windshield, but at least it lets you know.
In my opinion, if the a/c is on (for whatever reason) the a/c LED light should be on too, but this is certainly not the case, especially when auto defrost comes on for the auto climate control equipped cars.
Automatic climate control system defrost logic
1. Turn the ignition switch to the ON position.
2. Select the defrost position pressing defrost button ( ).
3. While holding the air conditioning button (A/C) pressed, press the air intake control button ( ) at least 5 times within 3 seconds.
The A/C display blinks 3 times with 0.5 second of interval. It indicates that the defogging logic is canceled or returned to the programmed status.
yes, I also had this same set up my previous Kia too, but I could not see much point to changing it (at least for me), the a/c removes moisture from the air in winter and clears up the windshield much faster and its not as if you are getting cold from the a/c when its in the heat mode on the temperature setting.
Also the big factor to not change it was the fact that in the manual it suggests running your a/c about once a month during to help maintain the system better, so this way I never had to remember to do it.