TLDR
What options exist for monitoring, diagnosing, troubleshooting, controlling CPU fan behaviour on NixOS?
My problem
For a while now, the CPU fan on my (NixOS) laptop keeps running forever, once it starts.
Specifically, when I wake the machine from suspension, the fan does not spin until the core temperatures reach the high 60s. Once it has started, the fan then continues to spin forever, even if the system becomes idle and the core temperatures drop: I regularly hear the fan spinning briskly without pause when the load remains around 0.25% CPU and all the cores’ temperatures have been below 53°C (with only the briefest of excursions above 50°C) for minutes on end.
When I suspend the machine and wake it, the fan is quiet … until the cores’ temperatures approach the 70s, and the then fan turns on permanently once more.
It’s starting to drive me nuts.