Hi, I recently bought a used 21” iMac (2010 Dual Core i3 3,06GHz iMac11,2) online to replace one with a busted graphics card. After receiving the machine I noticed that the CPU fan goes full blast mid-boot and stays on all the time. iStat Pro showed that the skin temperature and the HDD proximity temperature sensors were not providing any data which I think is the reason for the misbehaving fan. All other temperatures were within sensible range (20-40 C). I’m now looking for advice on wether I should try and fix the sensors or just return the computer. I know the skin sensor is quite easily accessible if I can find a replacement, but I have no idea where the HDD proximity sensor is located - it is not the one inside the HDD, right? Or could there be some other cause I’m missing? The computer came with High Sierra pre-installed, I wonder if such an old computer is even properly supported by this OS.