Open climate view in the centre display by pressing the symbol in the middle of the climate row.
Select the Rear climate tab.
Press 3rd row climate.
The air conditioning is activated/deactivated and the button illuminates/extinguishes.
The air conditioning for the third seat row is activated automatically if anyone in the third seat row puts on a seatbelt.
It is not possible to manually activate the third seat row's air conditioning if the main air conditioning is deactivated or the second seat row's climate control* is deactivated.