Question Fan spins but is not detected in BIOS, and RPM is not reported ?

[Shujee]

Here is my machine:

Case: NZXT S340 White
M/B: AsRock Z370 Killer SLI/AC
Fan: CoolerMaster SICKLEFLOW 120 ARGB

So I replaced one of original chassis fans with SickleFlow 120. After installing the fan I found that its cable was too short to reach the other fan header on MOBO. I then ordered a PWM Fan Splitter and was able to connect and run the fan. The problem however is that the BIOS (and any other software utility thereof) does not report the RPM of this fan. I tried using AsRock's Tuning utility and it can successfully run the "Fan Speed Test" (the fan changes speed as the test progresses), but no RPM is reported.

(As a side note, the fan supports ARGB, but my M/B has got no ARGB header, so I bought an external ARGB controller and attached it to my fan too. The RGB thing is now working correctly. Don't know if this has anything to do with RPM not being reported, but just thought I should share it.)

 

[hedwar2011]

1) Does your BIOS show the RPMs of the other fans and just not this one?

 

[Shujee]

1) Does your BIOS show the RPMs of the other fans and just not this one?

Yes, BIOS and Windows Utility both show RPM for FAN2 as well as CPU Fan. FAN1 used to show RPM when it was directly connected, but not with the extension cable now.

 

[hedwar2011]

Yes, BIOS and Windows Utility both show RPM for FAN2 as well as CPU Fan. FAN1 used to show RPM when it was directly connected, but not with the extension cable now.

This may sound crazy but maybe the extension cable simply provides power and not data...like some USB cables are for charging only and don't provide a data signal. There is usually 1 less wire bundled in that makes it like that.

 

[Zerk2012]

Yes, BIOS and Windows Utility both show RPM for FAN2 as well as CPU Fan. FAN1 used to show RPM when it was directly connected, but not with the extension cable now.

Those cables can only read data from 1 fan. If you look at the cable only one of the splitters should have 4 wires.

 

[Paperdoc]

I am guessing that you are using this Splitter as a simple extension cord, and have only this one fan plugged into it. So here's why you get that result, and how to fix.

Any mobo fan header can deal with the speed signal returned to it from only ONE fan. The speed signal sent back by the fan is a series of pulses, 2 per revolution. The header counts those to measure speed. IF you use a Splitter with two or more fans connected to a single header and that unit is made wrong, it will sent to the header BOTH of the speed pulse signals from two fans, and the header cannot count those properly. It gets wildly fluctuating readings and generates errors. So ALL Splitters (and Hubs) avoid this by sending back the speed of only ONE of the fans it feeds. Now, the speed signal is carried on Pin #3 of the connector, so the very simple means of doing this is that only ONE of the male output connectors on the Splitter had ALL four of its pins. All others are missing Pin #3, so any fan plugged into one of those outputs cannot send its speed signal back to the mobo header.

Look closely at the Splitter you have. Find the ONLY output that has all four pins. Make sure your fan is plugged into that output. Then your mobo header should receive its speed signal and show it to you.

 

[Shujee]

Thanks a lot, @Paperdoc and @Zerk2012 . This was exactly the problem. I have now plugged it into the 4-pin output and everything is working as it should.