The radiator fans should always be connected to CPU Fan 1 and CPU Fan 2 (or CPU Fan OPT) on the Motherboard.
Single Radiator Fan:
Connect the fan to CPU Fan 1.
Two Radiator Fans via Y-Splitter:
Connect the adapter to CPU Fan 1. CPU Fan 2 / OPT can be left unused.
Two Radiator Fans without Y-Splitter:
Connect one fan to CPU Fan 1 and the other to CPU Fan 2 / OPT.
Four Radiator Fans via Y-Splitters:
Connect one adapter to CPU Fan 1 and the other adapter to CPU Fan 2.
Its recommended that the pump be connected to an alternative fan header on the motherboard such as System Fan 1, Chassis_Fan 1, or for newer motherboards a dedicated pump header.
Please Note: Lowering the pump RPM can decrease the performance of the cooler along with increasing CPU temperatures.
PWM Y-Splitter: Designed to connect two fans to a single fan header. When using a PWM Y-Splitter, both fans connected should be identical models.