I was wondering if anybody already encountered the same problem. I searched the forums briefly and didn't find anything related.
I usually run my case fans - all of which are connected to the cases fan controller - at the lowest possible speed, as I hardly generate any heat inside the case. Then, yesterday, when I was working on my computer for several hours, all of a sudden, the 200mm top fan and the 140mm back fan spun up to maximum speed. I did not notice anything providing a proper cause. There was no way to get the fans back to a low rotation frequency. Though I did not expect it to work, but simply to rule things out, I tried changing the fan controller on the front panel to maximum and back to minimum, and I shut down the system, gave it some time to rest and rebooted. Didn't work.
I further noticed that this happened to just those two fans, while the two front fans remained unaffected. I could still regulate those. This makes sense, as both, back ans top fan, are connected to the fan controller with the brown cable, which has a Y-connector, and should thus be attached to the same voltage. The front fans have both individual connectors.
In order to rule out a fan failure I plugged the fans into the motherboards system fan connectors. I was able to adjust the fan speeds to a desired level in the BIOS ... eeh UEFI.
What might have happened? If a 3 pin fan has just 2 pins connected it behaves like a 2 pin fan, right? Could this mean, that the control pin/cable failed? But wouldn't that require at least some mechanical stress or ... something? How can I find out what is malfunctioning? Is there a way to fix it? (I purchased the case just 7 month ago so I should avoid invalidating my warranty)
If anybody has a clue, thanks a lot in advance!