Checked the computer with Malwarebytes Anti-Malware to make sure there isn't hidden crapware/malware that somehow uses a lot of CPU and hides from Task Manager.

Configure power settings to 'Power Saver' and cooling policy to 'Passive' (throttle the CPU before turning the fan up).

There's supposed to be controls for fan speed in the BIOS but those are completely missing. Failure to display CPU/GPU or provide options to configure them doesn't help either There's no way to disable 'Fan Overboost' (only options are 'Auto' and 'Overboost'.

Asus ROG 'Gaming Center' control panel.

GPU is running at 37 degrees C - nowhere near close to overheatĪttempted fixes so far (none of these fix the problem):.

Fan comes on full blast when the computer is idling (CPU usage around 1-2%).

Asus ROG 'Gaming Center' (monitor tool for CPU/GPU temperature and memory usage) shows CPU and GPU as '0', failing to detect temperature or memory usage for either.

Air coming out of the fan outlet vents is cold when this happens, indicating the temperature readings are probably false and the fan overboost is spurious.

Even if the temperature readouts are correct, 48 degrees isn't dangerous for a CPU and should not cause the fan to do this. The temperature readouts are a bit suspicious considering it's not a particularly fast CPU (2.2 GHz, no overclocking). I checked in the BIOS and the fan is running at 5000-7000 RPM while the CPU temperature is around 42-48 degrees (C, not F).

CPU temperature is reported as abnormally but not dangerously hot while idling.

Fan comes on full blast almost immediately after booting up and stays that way almost constantly.

Problem started about 4 weeks ago and I suspect it was caused by a bad Windows 10 update that broke something.

Bios fan speed control