To get the H100i system to work properly, you must follow the instructions provided with it. There are four electrical connections, and a software tool to use.
The PUMP unit of the H100i system is designed to use a fixed 12 VDC power supply and run full speed all the time. Control of CPU cooling is done by changing the speed of the two fans mounted on the radiator unit, and that part is done by the iCue software utility you must download and install.
The PUMP has one cable ending in a connector that must plug into a SATA power output connector from the PSU. It has another small cable ending in a standard 3-pin female (with holes) fan connector that MUST plug into the mobo's CPU_FAN header so it can send its pump speed signal back to that header to be monitored for failure. It has short cables from it ending in male (with pins) connectors and you must plug into them the cables from each of the two FANS on the radiator. Finally, you must connect a cable from a small socket on the side of the pump to a mobo USB2 header. This connection is how the iCue software utility can communicate its control instructions to the H100i system.
The iCue software does all control of the H100i system. You can use it to observe system operations and make custom adjustment to it if you wish.