For a week or so I have strange issue: sometimes my fan spins randomly with no CPU load (bar shows ~34 degrees Celsius). It spins as if I were compiling something really big (you know, 100% CPU etc). It also spins like that (very fast) for a second, then slows down, then spins again etc. Rebooting fixes this.
Hello,
Have you tried finding the culprit using htop?
Now you can mark the thread as solved. ;)
I would first take the appliance apart and clean it thoroughly.
htop wouldn't help if it's not due to cpu load, and op says their cpu load is very low when this happens.
I wonder, OP, could you boot into a live environment of a different distro and see if it still happens? It might be a software issue but it also might be something to do with your hardware.
Top CPU usage shown by htop was ~6% by htop itself :).
I tried booting Arch ISO from usb, but fan started spinning before OS was loaded (in "choose boot media" screen).
I cleaned the fan, applied new thermal paste and it's all good now. :D