Now this is an issue that has been driving me crazy for about two years now. I only recently figured out that it might be related to AMD drivers. It's gonna take a while to explain so please bear with me.
The way it started out was, every few months or so my CPU fan would stop waking up from sleep. By that I mean I would turn on my PC and all the fans would work normally, until I put it in sleep mode. After waking up, everything would work normally except for the CPU fan. It would spin up for a second or so, then stop completely. It would only start spinning again after rebooting my PC. And then it would stop working again after resuming from sleep mode and so on. Now the weird thing about this issue is, it seems to automatically fix itself in a day or two, after multiple reboots. Until it starts happening again months later.
After all this time, I still haven't managed to find a proper fix for this issue. I've tried replacing my CPU fan. Plugging a 3-pin fan into the cpu fan header seems to bypass the issue, but that's not a satisfactory fix since a low RPM 3-pin fan doesn't provide adequate cooling. I've even bought a new 4-pin PWM fan for my cpu cooler but that didn't fix anything. It did however show that the fan still receives power after it stops spinning (the LED light inside stays lit), it just doesn't get detected properly by the system. In the mean time I've also switched from a Radeon 7870 to a 390, but all the other hardware inside my PC has stayed the same. I've done completely clean installs of Windows multiple times, with different versions (from Windows 8.1 to the latest Windows 10 build 1607), but that didn't fix my issue at all.
I've almost given up on trying to figure out what's causing this problem until I noticed that one thing seems to trigger it reliably: installing new drivers for my graphics card. It doesn't matter if my CPU fan has been running without any issues for months, I can go uninstall all AMD software, then install the drivers again, reboot my pc and put it into sleep mode, when I wake it back up the CPU fan won't spin up. This happens every single time. Then the problem goes away by itself after a day or so. The problem isn't tied to a specific driver version, like I said it's happened numerous times throughout the last two years with different versions. Frankly I'm baffled as to how and why the GPU driver can even have any effect at all on my CPU fan, but it's happening.
Now that I've narrowed the problem down to Radeon drivers being the culprit, I'd like some further assistance. I'd really appreciate it if anyone can help me further diagnose and fix this problem once and for all.
-Gigabyte Z77-D3H motherboard
-MSI R9 390
-Windows 10 64-bit build 1607 (as mentioned it happens on previous versions of Windows too)
-Radeon Crimson 16.11.5 driver (the issue was present in multiple previous versions too. Haven't tried the new Relive drivers yet due to all the reported issues with the 390 series)