Sneaky A/C

I've found an annoing thing in my NB Miata.
Every time the ventilation knob is in either "windshield" or
"windshield/legs" position, the A/C turns on (when fan is on).
I have the same in my Camry, but only in "windshield" position and the A/C
light come on honestly.
Not in Miata - you can hear AC compressor but no light, no warning.
I do not see any reason to drive a Miata in winter with A/C on all the time
(since "windsh/legs" pos. I find most comfortable). I can control my foggy
windows turning AC just for few minutes.

The big question is:
How to turn it off??
I'd love to use my AC by the AC switch ONLY.

Maybe someone has a wire diagram for 2001 stick, AC, PS, no ABS, no cruise.

Best regards,
Kempi
'01 silverfish,IL