Impala has dual climate control. AC blows cold on

With a dual climate control system, it is imperative for a proper refrigerant charge to be maintained. the symptom you describe is a possible indicator of low charge on the system. the ac evaporator core is closest to the right side of vehicle thereby making air feel cooler on that side, on the left side of the vehicle the cooled air has farther to travel and warms up from cabin air before it discharged from the vents. this is the most probable issue for your vehicle...however if the charge is accurate, the issue would be more so in the air temperature doors which is located deep inside the dash...i hope this helps...good luck!