Afterinstalling a CPU cooler, your next task is connecting its cable to the CPU header. Without it, the fans won’t spin, which ultimately leads toCPU overheating.
In fact, most systemswon’t let you boot up. They will throw some forms ofCPU error messages.
Clearly, your processor fans must be running and for that, a dedicated motherboard connection is required. But other identical headers, likeCPU_FAN2orCPU_OPTmight confuse you.
Ever wondered what would happen if you connected the fan cable to a chassis/system/pump header? Let’s find out.
CPU Fan Header Pinout – A Brief Overview
Most modern motherboards embed 4-pin headers but the older ones may only come with three pins.
The main difference between them is the extra fourth pin, which offersbetter speed customizationusing pulse-width modulation(PWM). DC fans(those with three pins) usevoltage changesto regulate the speed. Meaning, it doesn’t offer as precise control as the former.
Despite the differences, you may still connect a 3-pin to a 4-pin connector and vice versa. Just understand that the fourth wire will remain unutilized and thePWM fan will work in DC mode.
The pinout I’m referring to isn’t limited to CPU_FAN. This case holds true for all the fan headers. Let’s take a closer look at it:
To connect your CPU fan to the motherboard, it’s essential tomatch the male and female plugs. The ground connector of the fan cable should align with the ground pin of themotherboard header.
Usually, most fan cables follow a standard color coding to differentiate the wires. Ground is alwaysBlack, +12V can beRed/Yellow, Speed Sensor isYellow/Green, and PWM should beBlue.
Fans generally consume200 to 300mA current. This means any header can provide enough power for them to run.
Technically, you may connect your CPU fan to even theOPT_FANorSYS_FANheaders. Joining case fans toCPU_FANis also acceptable.
But that’s definitely not the thing that professionals do. Manufacturers have a purpose for why they have assigned separate headers. So, the question stands – which header to choose and when?
When to Choose CPU Fan and CPU OPT?
In most motherboards, you’re only going to find oneCPU_FANheader. Even if you notice similar indications, likeCPU_FAN2orCPU_OPT,these are different!
The thing is –your BIOSintegrates related speed settings for each header. So, if you connect your CPU fan to anOPTorSYS/CHAheader, it won’t be recognizedduring the POST. And, thus, the‘CPU FAN Error’pops up.
The same case happened to our team whenreplacing the CPU cooleron one of our ASUS setups. Even though the fan was spinning, we later realized – it was mistakenly connected to the optional header.
It’s possible tobypass this messageby simply running theBIOS setup and exiting. To permanently get rid of this issue, set theMinimum Fan SpeedtoIgnore. The particular option variesbased on the motherboard.
However, this is just too much to ask for! So, the best approach has to be connecting the fan cable to the relevant header. That said, I always recommendCPU_FANconnector for your primary cooler.
And if there’s an additional fan (as with thetwin-tower heatsink setupdemonstrated below), go forCPU_OPT.
In awater-cooled/AIO setup, you’re going to get a relevant 3-pin header for the pump (orSYS/CHAheader). The 4-pin cable (for radiator fans) should go into the CPU_FAN header.
Note:The RGB connectors do not require a fan header connection. you may insert them on dedicated RGB or ARGB headers. For that, here’s a guide to help youconnect RGB fans to the motherboard.
Connecting CPU Fan to Motherboard Header
Now that you’re aware of the importance of CPU fan header, let’s get into the basics of how to connect it. The following instructions should be identical for every other fan connector as well:
As you may see, the connection procedure isn’t a tough task at all. Generally, the fan cables are short and it shouldn’t add any burden duringcable management.
However, it becomes a little challenging when connecting radiator fans. you may utilize afan splitter/hubif the boardhas one CPU_FANand not even a single optional header. Note that any mistakes might cause theradiator fans to stop spinning.
Controlling CPU Fan Speed
No matter where you have connected your CPU fan, the idea ofcustomizing fan speedis pretty much the same.
However, the exact steps varydepending on your model’sBIOS pageorOEM software. Our team has accumulated dedicated guides for the most popular motherboards here:
Circling back to the previous discussion on choosing the right header, this is where it’s the most relevant.
It’s completely fine to connect your CPU fan cable to even anOPT/SYS/CHA/PUMPheader. But you’ll havetrouble controlling the speedas thecooler won’t be detected in the BIOS. Instead, it will be discovered under theSYS/CHA/PUMP section.
But why would anyone connect to the wrong motherboard connector? Well, we might actually need to do that in some extreme scenarios.
Speaking for myself, the pins got bent on myMSI MAG 550M MORTAR. Since the CPU fan wasn’t detecting, I had no other choice than to utilize the optional header.
So,inMSI Click BIOS, I had to control the OPT header to tweak the speed of my CPU fan. And yes, I even disabled theCPU Fan Fail Warning Controloption to get rid of the error.
Note:Fans connected to aMOLEXordaisy chained to a splitterget direct power from the PSU. Since it has no connection with the motherboard, there won’t be an option to control their speed.
