Motherboard not recognizing front fan

daneshL_ · Sep 8, 2017

Hi,

I have just build my first pc. However, my coolermaster front fan is just not recognized by the motherboard. And I've tried using both chasis fan connector to see if either one is broken, but that was not the case. I will post some pictures of the connections with the fan and the mobo.

Mobo: Asus prime b350plus
Fan: Coolermaster sickleflow 120mm

Am I doing something wrong? Thanks in advance.

https://www.dropbox.com/s/rdyobxzk8oh6et6/0c248137-958c-4ace-b128-7525d5a7f059.jpg?dl=0
https://www.dropbox.com/s/mgm2b4wl6fzueyt/8db4f369-7080-4428-afde-14c25ffb2790.jpg?dl=0
https://www.dropbox.com/s/itehdzrfmqy338p/689fe388-c23f-4199-8a52-616c9f8feb16.jpg?dl=0
https://www.dropbox.com/s/5bb0qv3n4fpgnzs/a8246c34-df67-4825-a6e8-84f1c0c13711.jpg?dl=0

Sedivy · Sep 8, 2017

Wait....why is there a molex adapter in there at all? You should be connecting the fan directly into the motherboard, no molex connections needed. If you connect it directly to the PSU via molex, it'll always spin at highest voltage (no voltage regulation) and so nothing motherboard can do about it.
You need to connect its 3 pin directly to the 4 pin fan header on the motherboard.

daneshL_ · Sep 8, 2017

Sedivy :

The cooler came with a 3 to 4 pin adapter which interconected with a molex, so nothing connected to the psu.

Sedivy · Sep 8, 2017

...but molex is connected to the psu? There's nowhere else for molex to connect to. If you follow it, does it not lead back to psu? Unplug the fan from molex, and just connect to motherboard directly.

Paperdoc · Sep 8, 2017

It is not clear what you mean when you say your "front fan is just not recognized by the motherboard". Do you mean the fan does not run at all? OR, that it always runs at full speed. Or, at some other fixed speed? Or, does it run normally but the mobo can not show you the fan speed?

I am presuming you have a Coolermaster case and that fan is supplied with the case and re-installed. Exactly what case model is that?

That thing with the unused Molex connector on it is NOT needed, so you should remove it. You do NOT need an "adapter" to connect a 3-pin fan female connector to a 4-pin fan male connector. The end of the white cable you have plugged into the "adapter" can plug directly into the black connector on the end of the black cable. Now, what those two cables are and where they connect to is another question, and that's why I asked exactly what case you have.

For a mobo to "detect" and control any fan, it MUST be plugged into a mobo fan header. If the fan is connected somewhere off the mobo, the mobo has no way to know about it.

Paperdoc · Sep 13, 2017

Thanks for Best solution. We're still interested to know details of your system, and whether or not you have found a solution. Maybe you need more help?

daneshL_ · Sep 13, 2017

Paperdoc :

At the specifications of the coolermaster fan was stated that is was a 3 and 4 pin fan. So I thought it should be able to have the PWM function, but with an adapter then. But that was not the case.. It said 3 and 4 pin because there was an adapter with it shipped so that you can ONLY connect the 3pin connector to a 4 pin receiver. But thanks for the response, I didn't have enough sleep that night

.

My build:
https://pcpartpicker.com/b/G2kdnQ

Sedivy · Sep 13, 2017

Ah no, the 3 pin fan always runs just as a 3 pin fan. The voltage regulating wire is not there, and it's differently controlled. Voltage fans spin faster with higher voltage while pwm fans are always at 12V but have intermittent connection regulating the speed. In other words they are not interchangeable and can't really use an adapter.
Both 3 and 4 pin can be controlled speed wise, though 3 pin are less responsive than 4 pin ones. It only needs adjustment in bios, so that mobo knows whether it's a voltage fan or pwm fan (to know what voltage/current to supply) so the fan header can differentiate, and then you adjust your temp/rpm curves within bios.

Paperdoc · Sep 14, 2017

Fans spec'd as 3-pin and 4-pin are confusing and a little deceptive. The two fan types require different mechanisms of control from the mobo header. Some mobo headers can be configured for either type of control, and come cannot.

The design of 4-pin fans included as much backwards compatibility with the older 3-pin design as they could. Electrically and mechanically, the connectors for the two types all fit together, so you CAN plug one type into the header for the other type, and it will work - sort of. A 4-pin fan plugged into a 3-pin header WILL be under speed control using the older Voltage Control Method, even though that is not quite as good as the new PWM system. A 3-pin fan plugged into a 4-pin header that really does use PWM Mode for control will always run full speed - no control. But that gives you good cooling, just not with speed control. So, fan makers can tell you both fan types
CAN work with either header type, and they are correct within those limits.

There's another "version" of this, too. Some fans come with an adapter that allows you to connect to a 4-pin Molex power output connector from the PSU and "convert" that to a standard 3-pin fan male connector. Then you can plug either fan type into that. The limit here is that a PSU output does NO control at all, so the fan will always run full speed. Moreover, the PSU has no way to feed the fan's speed signal back to the mobo, so you will never "see" the speed of a fan connected this way.

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