Identify the functions separately
Air conditioning, automatic temperature control and separate temperature zones describe different capabilities. Rear vents do not by themselves prove that rear passengers have independent temperature control. Check which controls are available at each seating position.
Try the controls while parked
Ask the seller to show how temperature, fan speed and airflow direction are adjusted. Follow the vehicle's instructions and avoid running a combustion engine in an enclosed space. Note whether the display responds and whether the controls behave as explained.
Account for the viewing conditions
A brief check in mild weather is not a complete assessment of heating or cooling performance. Do not infer a fault or full working condition from one short observation. Record what you tried and the conditions under which you tried it, especially if a function was difficult to assess.
Keep equipment and condition separate
An equipment description can identify a climate function but cannot establish that it currently performs correctly. Note unusual noise, warning messages or unexplained behaviour and ask for inspection if necessary. Do not dismantle vents or attempt to handle refrigerant. When comparing cars, distinguish confirmed controls from untested performance so that a broad climate package label does not hide unanswered questions.