Pedestrian_A

If you are talking the rectangular button on the left side, that's the rear defroster.  The lower left rotary switch is the vent position for air/heat blower.

I assume you pressed the A/C button while the fan is on but the A/C button light is not on.  Are the vents blowing out cold air?  If not, the A/c needs to be recharged with refrigerant.