I know this has been posted about before, but I don’t see a solution.
After upgrading to TrueNAS Core 13, I now get fan sensor error messages. Clearly something is broken or the motherboard isn’t compatible with the fans I have because they keep dipping to a reading of 0, then back up, then back down. I tried lowering the threshold, even to -1, but that didn’t work. I tried changing the fan settings in the IPMI tool on my Supermicro X11SSM-F motherboard, but that didn’t do anything. I’m getting alert emails every 5 minutes. Do I have to turn off all alerts and then have no visibility into alerts that do matter? Should I replace all the fans to see if I can find a compatible one? The problem is, I’ve seen posts about Noctua fans doing the same thing, and that’s the brand I would go to. Even if this is a broken fan sensor, I’m not replacing the otherwise perfect motherboard to fix that. Has anyone figured out another option to turn off fan sensor alerts?
A few stupid question that may do nothing to solve your issue; 3pin or 4pin fans? Is it all the fan ports having this issue or just 1? Are they all connected directly to the motherboard or using splitters? If splitters, do they turn the 4 pin connection into 4pin for 1 fan (master) and 3pin for the other fans (slave) or do they all have 4 pin connection? (I’ve seen the second type of splitter cause issues as multiple fans report different speeds due to variations in tachometers).
These questions kind focus on only the hardware side of things as I have no clue on Core/Bios settings for this. Only BIOS related guess would be to check if the fans are correctly set to PWM or DC.
I have fans plugged into FAN1, FAN2, FAN3, and FANA and all but FAN2 generate the error. None have a splitter, but I don’t recall which have 3 pin vs 4 pin connectors. The only BIOS setting I could find that has any impact on this would be to completely turn off alerts in the BIOS, but that would disable any hardware-related alerts.
…my very lazy fix would be to run splitters on fan 2 depending on supported amperage & power loads of the fans
Edit: or move fan2 around & see if it is faulty fans
OK seriously that suggestion is so…. yeah that’s a great idea. 
I love it! I’ll give that a shot!
