That's when it clicked. The fan wasn't broken. Windows simply didn't know how to control it because the driver was missing. The laptop was running a "safe mode" fan profile: ON all the time.
Right-click → Update driver → "Windows couldn't find drivers." Standard.
I searched online and found nothing but old forum threads. One said, "It's a dummy device, ignore it." Another said, "Your laptop will explode if you don't fix it." Very helpful. acpi\sny5001 driver
A few years ago, I bought a used Sony VAIO laptop. It was a beautiful machine—sleek, magnesium-alloy body, a gorgeous 1080p screen. But within an hour of using it, I noticed a problem: the fan was always on. Not loud, just a constant, low whirrrrr that never stopped, even when the CPU was at 2% usage.
I went back to Device Manager. The yellow triangle was gone. had moved to "System devices" and was now named Sony Firmware Extension Parser . That's when it clicked
Then, deep in a 2012 VAIO support thread (archived, in Italian), I found a real clue: "SNY5001 is the Sony Firmware Extension Parser. Without it, Windows can't talk to the EC (Embedded Controller) for fan curves and battery health."
And the fan? Within 30 seconds, it spun down. Then stopped completely. Dead silent. It only came back on when the CPU actually heated up—exactly as it should have from day one. The laptop was running a "safe mode" fan
I installed it. It took 10 seconds. No reboot needed.