AC on with Defrost

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FC, FE, Mazda5
I noticed that in my 2012 Mazda5 that the AC will turn on automatically when the air blend selection is set to front defrost (so either front defrost on its own or while also blowing on your feet, accessed through either the defrost dedicated button or through the air blend mode selector button). It does this automatically, regardless of the "AC" button, and does not light up the LED in the "AC" button. I would prefer that the AC not automatically come on when defrosting - there are plenty of times where I want the air blowing across the windshield but don't need the parasitic drag and hit to fuel economy caused by running the AC.

Is there a way to accomplish this (so AC comes on ONLY with the AC button pressed, not automatically with defrost), short of wiring up a manual switch to the AC compressor?
 
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South Carolina
:
12 MZ5 13 CX-5
Defrosting the windshield is far more efficient using AC than just blowing air. That's why it automatically turns on.
 
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FC, FE, Mazda5
Yes, defrost works more quickly and effectively with the AC on since that dries the air coming out the vents so it can pick up more water vapor, and I would still use it that way sometimes when it is necessary (like just starting with a foggy windshield).

However, I would also like to direct the air up towards the windshield for in-direct cabin airflow at times when defrosting isn't necessary (so no AC needed), or use the defrost without AC just to help keep the windshield clear like I wanted to do on a road trip recently where I was driving as the sun was going down and the outside temperature was gradually falling, causing a slow condensation on the inside of the glass. In that scenario, constant airflow across the windshield would keep the condensation from forming even without AC, so no need to take the fuel economy penalty or keep switching back and forth between defrost and face vents.