Laptop fan still working after computer is turned off Lubuntu 21.10

Hi guys,
I have a dell Inspiron 5555. i use the shutdown button on the menu., but even after the laptop has shutdown the fan keeps running/
is there any quick diagnosis I can run?

I don’t know your box/device, but I’ve used boxes that keep the fans running until the box has cooled, being operated by the box firmware itself - completely out of control of the installed OS. If the box was used for a long time, especially in warmer/hotter weather, it could take some time before the fans turned off.

To see if the Linux kernel was still running, I’d normally use SysRq commands to direct the kernel to perform functions (REISUB or reboot for example) to see if it responded; alas a normal install of Lubuntu 21.10 has this feature disabled.

— later addition/edit

Also asked at Laptop fan still working after computer is turned off Lubuntu 21.10

I also remembered

On one box; replacing the fan made it turn off faster (it wasn’t spinning well it turned out, it was the fan spinning for longer that made me look at why & finally realize the fan was dying…)


That was my guess too.
Does the fan eventually stop?

On the thinkpads (example where replacing the fan sped up fans turning off) & most boxes yep; fans stop (eventually).

I’ve an old Nokia box to my right on this desk where the 3x fans drop to only 1 which remains on whilst power is connected; but it’s a rack-mount box thus it’s supposed to operate this way I gather (I flick the socket power switch off when I don’t want the white noise). I’ve encountered other boxes that operate this way, but not laptops.


FWIW, I’ve had a laptop that kept the fan on until it was cool. I want to say it was Toshiba with an Intel CPU. This behavior could be disabled by going into the BIOS and finding “Cooling” - which, and my memory is really fuzzy, was under CPU options in the BIOS.

I’ve seen it also in desktops, usually the kind that have fairly expansive BIOS options from which one might overclock or whatnot. I haven’t seen that in a while, as I’ve just purchased fairly generic, pre-built PCs for ages.


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