511 CPU fan not detected error

[roman_mk]

Somehow I noticed my CPU fan isn't working while I'm using my PC. CPU temperature is 70/80 degrees and the cpu-fan does not work, it starts to work when the temperature stays over 90 degrees, it still works on max speed for maybe 10/30 second and stops again untill temperature isn't 90 or more.

Speed Fan app can't find my fan and can't change speed, nothing happens. BIOS doesn't show my fan, it's looks like "n/a" in power thermal settings. But I know my cpu-fan isn't broken because I saw it works, and when I start my PC it spins maybe 1/2 second and then stops. Please help me, no noise is fun but I worry about my CPU temperature. Sorry for any mistakes, English is not my native language.

[DGroves]

the first thing i would do is to replace the cpu fan as it's a cheap item and rules a item off the possible bad checklist

remove the fan, then using a can of compressed air make sure the cpu cooler fins are free of dust

now look at the fan, on one side will be the fan maker and the fan model number, google using this info and you will find numerous sites selling fan replacements

install the new fan and report back if that resolved the issue