Linux doesn't recognize replacement CPU fan - gives CPU cooling fan failed- shuts down


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I’m using Mint 20.1 – Cinnamon.
The main reason for replacing the CPU fan is, one blade has a hairline crack.  It’s not flopping around, but I’m concerned about tempting fate.  Cooling -wise, it’s doing well for now.  

I'm not sure if it could be repaired (reliably), and not be out of balance.  Maybe doing the "same thing" to a blade opposite the repaired one.


NOTE:  There are no BIOS fan controls for me, so that can't be used for speed control of any new fan.

I bought a replacement, "Arctic F8 PWM PST", (80 mm, 4 wire - just like old fan) at reputable, local repair & sales shop.  I'm now wondering if the fan is a suitable replacement for a Quad Core CPU?
Some specs (not where I bought it):  Main thing seems to be its quite low MIN 300  RPM & possibly lower MAX 2000 RPM than might be needed at times, vs. the old fan.

Plugging it into the mobo "CPU Fan" 4 pin socket (only 4 pin fan socket on MOBO), boot up, immediately says, "CPU cooling fan failed.  Shutting system down in 4 seconds"  And it does.

I read a lot about using ('nix CLI tools) lm-sensors, "sensors-detect", PWM settings & lots of related info.  I know enough now to be dangerous.


1st issue is help deciding if the Arctic fan is a suitable replacement for CPU, spec - wise.

I can only find some specs on old fan, "Delta / Cooler Master AUB0812HV, 80mm, 4 pin (no other characters in the model #).  I've seen specs it has MAX RPM around 3600.  I haven’t found the MIN RPMs anywhere.  That may? be part of the problem. The Arctic may be defective - not sending / receiving data, or its current 300 RPMs are perceived as failing / failed.  I have no idea how to get around that, as everything I've seen to have Linux (or whatever) recognize & use a new fan, much less set a min. RPM, needs running some commands.  I don't know how to do that in 4 sec.  I'm not sure if that level of changing settings - in the ALREADY installed Linux (running root cmds) can be done successfully from a Live DVD / USB, making changes to installed distros?


Either installed or testing on workbench, the old fan's RPMs are much higher than the Arctic fan.  I can only observe the relative speed of each fan - on a bench, applying 12V to -Blk & +Red wires.  Arctic fan's specs are 300 - 2000 RPMs.  On the bench or installed - for a FEW seconds - before system shuts down, it spins VERY slowly (300 RPMs?) vs. the old fan.


Testing the old fan w/ 12V, it spins several times faster & according to "sensors" (part of package "lm-sensors") or Psensor GUI, it starts at around either ~ 1650 or 1070 RPMs (depending on which Fan (1 or 2) is CPU fan.  Only 2 show RPMs - assume the 2 plugged into mobo.  Two other fans detected don't show RPMs.  I'm "guessing" the 80 mm CPU fan would be the higher RPM vs, the other 120 mm case fan(s).  The RPMs of the 2 don't vary much. Nothing I've seen in any files identify any of the fans, except Fan1, Fan2..., or /device/pwm1, pwm2 & so on.


When applying 12V to variable speed fans on a bench - to Blk & Red wires (or neg & pos, if all black wires), I don't know if the resulting speed is its MIN, MAX RPM (or something else).  Seems clear, the Arctic has considerably lower (300) MIN RPM, and AFAIK, a much lower (2000) MAX RPM than the old fan.


So, if I manage to find an 80mm PWM fan with RPM range closer to the old fan, would that greatly reduce / eliminate problems of replacing the CPU fan?  I'm only guessing, if a new undetected fan had RPMs closer to the current, it might not shut down the system.  I can't see everyone replacing a simple fan having to go to this much trouble.

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Your BIOS has to detect it before Linux can use it.


Are you sure the CPU fan is in the correct "CPU_Fan" header?


I think you might need a BIOS reset...

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What is the brand and model of the motherboard you are plugging the CPU fan into?




Aryeh Goretsky


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  • 2 weeks later...

@ goretsky:  It's an HP board made by Asus - for HP.  It has a meaningless name / model.  There are very few specs for it - I looked for yrs.  Nothing like the mobos produced for OTC retail or custom rig builders.


@M/M:  Yes, I'm sure it's plugged correctly, into the (only) "CPU Fan" header on the mobo.

I understand that BIOS or some chip on the mobo must detect, or be sent a signal that a CPU fan is present & by whatever criteria, think it's operational.

The question really was, is it very common to have to "setup" a new fan so that BIOS or other means will detect it. 


I can now say, that in Mint & probably Ubuntu -maybe Debian, installing a properly functioning CPU fan doesn't normally require setup / config,  Not just for the fan to be recognized.

If you want tight fan speed control at various CPU temps (only the CPU, here), then it may require some setup, using tools in the Linux lm-sensors package.


Someone mentioned that the NEW Arctic fan's function to send a signal to BIOS may not be working.  Even though it was new & not a low price brand, that sounded like a good place to start.

I switched another 3-pin fan that plugs into mobo over to the CPU fan header.  There's a tab on the mobo to guide how the connector is positioned.

With 3 pins vs. 4, it would be detected & speed probably can be PWM controlled, but it won't report RPMs.  BIOS was fine with that fan plugged in & booted normally.


That probably meant the new Arctic fan had a partially bad PCB or loose connection on the wire or circuit that reports its presence.  The fan may not have responded to a PWM signal and / or the resulting low RPMs didn't meet some requirement (in BIOS?).  Not sure.  I just decided to order a different fan - a Noctua, with higher MIN & MAX RPMs & better noise specs than the Arctic.  I put an extra 3-pin, 120mm fan on the CPU heat sink until the ordered fan arrived.


It was recognized right away & either the CPU sends a temperature to "fancontrol," or previously configed PWM settings start it around 800 RPM.  It doesn't go much higher unless doing something CPU intensive.

At that speed, it's virtually silent.  I cleaned & lubed the other (4) fans & just browsing or viewing sites w/o massive graphics, I can barely tell the PC is on.


Years ago, someone turned me onto "Super Lube" by Synco Chemicals, for small fans (computer, desk fans, etc.) & applications you don't want to re-lube very often.  I did some research & read reviews before giving it a try. 

It's a synthetic, clear, light weight grease w/ PTFE (teflon).  Doesn't dry out, like small motor oils & light petroleum based greases.  Says temp range -45 F to +450 F.  Also dielectric & "non-toxic."  Can use as lip balm, in a pinch (kidding - I wouldn't).


I lubed a different case fan that started making some noise several yrs ago.  I tried to clean any remaining lubricant in the center hole of the sintered metal bearing (assume wasn't much left).

Put a film on the fan shaft & some in the shaft opening.  That was several yrs ago on a fan that runs constantly at relatively high RPMs.  It hadn't dried out or liquefied & run on the fan frame.   Spinning by hand or testing it on a bench w/ 12V source, it still spun w/ almost no friction, but I put a little extra in, since I had it out.  And remember, WD40 is not a lubricant.  It will make small motors or fans turn easier - for a bit, but it dries out way too fast.


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