Only CPU fan and USB sockets, how can I install a liquid cooler?

If you don't have a free USB header on your MoBo, you have a couple of options.

1. NZXT makes a neat little internal USB hub. I had to do that with my full ATX build so no worries. It works great and you can plug up to three things into it and it will run off a single USB header on your MB. The Hub does require a Molex power connection though, so you will need to make sure your PSU has a Molex connection.

2. The Link cable is nothing more than a USB 2.0 Mini-B (not micro-usb), or at least it is on my H115i. I have not tried it but in theory you should be able to plug any Mini-USB (again not micro) cable into the pump and then to an external USB 2.0 port on the motherboard to give you control of the pump.


The fans on the other hand should be simple. The pump should have a splitter for both rad fans to plug in to and there should then be another 4-pin connection that will plug into the CPU_FAN port on your motherboard. The fans will be controlled by the CPU port NOT the Link cable. So if you don't have the link cable you will not be able to control pump speed but you still should be able to control the fans.

You cannot use the Corsair Link utility with this model from Corsair. The ONLY reason for the connection to a mobo USB header is for using that software, so forget about the USB thing entirely.

The H75 is a simpler system than some other Corsair liquid coolers. The PUMP unit is designed to run at full speed all the time, and it has its own connector (3-pin) that goes to a mobo CHA_FAN or SYS_FAN header. You have not told us what headers of that type are available in your machine, and the MSI website tells us nothing about the mobo inside it. If you can tell us the model number of that mobo, we can look up its manual to check details. However, IF you have an unused CHA_FAN or SYS_FAN header, plug the pump unit into that. Then, in BIOS Setup after it is all hooked up, try to configure that header to use PWM Mode for control of its "fan". If you can do that, it will ensure that the pump always receives the full 12 VDC supply it needs. If there is no option for that, configure that header to the Profile for constant full power. On the other hand, if you have NO unused SYS_FAN or CHA_FAN header to use, you may have to change to a different Splitter on the CPU_FAN header.

Now, assuming you can connect the pump unit that way, the H75 system design assumes the two RADIATOR FANS will be powered and controlled entirely by the CPU_FAN header. To do this they supply a two-output 4-pin Splitter, That has confused you a bit. Any mobo header can accept the speed signal from ONE fan - two or more causes it total confusion and errors. So the Splitter merely does NOT connect the speed signal from the second fan, and it does this by NOT having a Pin #3 in one of its outputs. This has NO impact on the ability to control the fans. So, use the supplied Splitter to connect both radiator fans to the CPU_FAN header. In BIOS Setup check, but I expect it will already be configured properly by default. It should use the "Standard" or "Normal" control profile for automatic fan speed control, and the PWM Mode for these 4-pin PWM fans.

IF you do NOT have an unused mobo CHA_FAN or SYS_FAN header to devote to the pump connection, post back here for advice on how to get and use a different Splitter so you can connect the pump and the fans to the CPU_FAN header.

OK, if you have only a free CPU header for fans, here is how to connect both radiator fans AND the Pump to the CPU_FAN header. First you need a 4-pin fan Splittter that can provide three outputs. Here's an example

https://www.newegg.com/Product/Product.aspx?Item=N82E16812423163&cm_re=coboc_fan_splitter-_-12-423-163-_-Product

You do NOT need a HUB. That is a different type of device and it can be distinguished from a Splitter because a HUB has a third type of "arm" that must plug into a power output from the PSU. Just get a Splitter of the 4-pin design. Plug its female connector into the CPU_FAN header. Plug one of the radiator fans into the only output arm that has all four pins so the BIOS will show you the speed of that fan. Plug the other radiator fans AND the Pump connector into the other two output arms. In BIOS Setup, ensure that the CPU_FAN header is set to use PWM Mode.

A Splitter feeds all of its fans from the mobo header, and hence there is a limit. The header can only supply up to 1.0 A max current. Your rad fans are spec'd at 0.18 A each, and I am sure the pump will not use more than 0.5 A, so the total is OK. The two fans are both PWM type, so their speeds will be controlled by the CPU_FAN header. The pump actually behaves as a 3-pin fan, and here we are taking advantage of what happens when we connect a 3-pin fan to a 4-pin system using PWM Mode. In that mis-match case, the 3-pin fan (well, here it's the pump) will always run at full speed with no control. That is exactly what this pump is supposed to do, so it all works.

Doing it this way involves a small compromise on safety. One of the important things the CPU_FAN header does is monitor its fan's speed signal for FAILURE. If it gets no speed signal, it sends out an alarm that the CPU fan has failed. On many mobos this also will cause the system to shut down very quickly to prevent CPU chip overheating, without even waiting for the temperature sensor inside the CPU chip to show a high temp. My recommendation above has one of the radiator FANS providing the speed signal for that port to monitor. A failure either of the other fan, or of the pump, will NOT be detected, and protection of the CPU from failure will rely solely on the temperature measured inside the CPU. If you think that is too risky, change the way the items are plugged into the Splitter outputs. Plug the PUMP into the one output that has all four pins, and the two fans into the other arms with only 3 pins each. This will allow the CPU_FAN header to monitor the pump unit for failure, and the fans' speeds will never be displayed or checked, but they WILL be automatically controlled properly. This may be the safer way to do it. At least if the pump is guaranteed not to have failed, you have some cooling going on, even if one or both fans has failed. Whichever way you choose, you should realize that, when you connect more than one device to a fan header, it cannot monitor all of those devices for failure. So it is up to you, from time to time, to check those devices (say, the two fans) and verify they are still working.

Thanks for Best solution, and good luck.