HP Envy x360 fan control thermal sensor bios bug (F23)
HP Envy x360 AY series - F23 BIOS.
The bug:
The laptop's skin temp sensor (infrared thermal sensor) freezes and stops updating the temperature.
In this example it got stuck at 25c. This causes issues for fan control. We can see that during a benchmark the machine sat at 100c for almost a minute with the fan completely turned off.
To fix:
Restarting the machine does NOT fix the issue. I restarted the machine on video. Only shutting down / hibernating the machine fixes it.
This leads me to believe it is a firmware bug.
Chapters:
0:00 Introduction
0:20 Temperature read outs
0:57 Benchmark starts
1:15 CPU hits 100c with fan off
2:08 Fan starts
2:26 Stop benchmark, allow laptop to cool
2:58 fan abruptly stops
3:28 Restart laptop, skin temp reading same
4:10 Boot laptop from hibernate
4:25 True CPU skin temp reading