Question RGB fan working but LED not turning on

Jan 17, 2022
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Think I did not put the cord in the right spot. Using the Corsair 5000D Airflow Tempered Glass Mid-Tower ATX PC Case. Referring to the 3 fans located on the right side of the case if you're looking at the case from the front (side without see-through glass).

Using the Corsair ML120 PRO fans.

Any suggestions? Thank you!
 

Paperdoc

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First, I presume you have the ML120 PRO RGB fans, and not the non-RGB ones. If you bought a three-pack they should have come with two boxes required for lighting power and control. For each fan there is a cable for the MOTOR only that powers and controls the fan function. But there is a separate cable for lights.

There is a Lighting Node Pro, I believe - a box with two cables that go from Node Pro sockets to a mobo USB2 header and to a SATA power output from the PSU. Then it has two other sockets for connection to the second box (uses only one of these two) called a RGB LED Hub. This box has one input socket for connection to the Node Pro, another socket for power input from a PSU SATA power output, and six output sockets for the lighting cables of fans. You must connect the fans into those sockets in sequential order - use sockets 1, 2 and 3 only in your case for 3 fans. Once that is all done you must install and run the Corsair software utility iCUE to configure the lights.

Some Corsair packages now contain a slightly different lighting control system consisting on only one box that combines the functions of the Node Pro and RGB Hub, but I am not sure which system you have.
 
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Paperdoc

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Thanks for the photos, they make this clearer.

That appears to be an older set of Corsair hardware. The easy part is the fan MOTORS. They all connect to the small board in Photo 3 with the label "PWM Repeater". It simply takes the PWM signal from a mobo fan header (MAYBE the one circled in Photo 4) and relays that to all the fan MOTORS plugged into it. It also has a four-wire cable from its other end that I presume goes to a SATA power output from the PSU to supply power to those fans. I say "MAYBE" because it looks like the circled fan header may be the CPU_OPT header. If you tell us the mobo maker and exact model we can look up details on that. CASE ventilation fans generally should NOT be connect to the CPU_FAN or CPU_OPT header for control. Those headers use a temp sensor inside the CPU itself for guidance, and thus are suited to govern cooling of the CPU chip. Elsewhere on your mobo there will be CHA_FAN or SYS_FAN headers guided by a different temp sensor on the mobo. If ALL of the fans connected to this "PWM Repeater" board are for the CASE, and none of them for the CPU specifically, the board's cable should go to one of those other mobo headers.

Back up to the first two photos. That box labelled "Corsair RGB Hub" is actually the Controller that provides both power to lights in the fan frames and control of their display patterns. The two-wire cable from its left end gets power for it from a SATA power output connector form the PSU. The 3-wire cable from its right end should NOT go to any mobo header. You have it plugged into a mobo 4-pin plain RGB header according to Photo 2. DISconnect that. What is missing is a second box with three buttons on it. See the manual for a similar fan set here

https://www.corsair.com/corsairmedia/sys_master/productcontent/HD120_RGB_FAN_QSG.pdf

which shows that system on pages 3-5. Many more recent designs have a way to feed a mobo lighting header's signals into the Controller box so they can take over control. But this box can NOT do that. It is designed ONLY to accept simple pushbutton signals from its own hand-held 3-button box as supplied. So, disconnect the cable from the Corsair RGB Hub at the mobo RGB header, and plug that instead into the socket on the 3-button manual control box. Then use the buttons to make changes to your lighting displays.