Genuine Daikin 2P390936-1S Indoor Heat Exchanger is the indoor heat-exchanger coil that transfers heat between the refrigerant and the air passing through the indoor unit. When it is damaged, blocked, or leaking, the unit can lose output, heat or cool poorly, or lose refrigerant. A genuine heat exchanger fits and performs the way your Daikin expects — where a non-genuine part can flow wrong or fit poorly.