Quote Originally Posted by gtj View Post
There should be no scaling in sensors.conf. The driver outputs the correct values for voltage, temp and rpm directly. I'll look at the 3.0.1 version and see what it's doing but now that I think about it, they look actually correct for the Bonetrail and a QX9650, especially when idle. I may have been thinking about the XBX2.

Are you sure you have the rear fan plugged into the correct header on the MB? There are 2 in that general vicinity. The one behind the audio stack is the MCH fan and isn't monitored or controlled. The one behind the mounting hole next to the audio stack is the rear fan header.
My case is such that I can get close enough to read all the labels on the motherboard so I'm sure about which header is which.

Anyway I investigated a bit more and discovered a curious thing -- I do see an RPM reading for some fans but not others: the RPM sensing seems not to be working for all kinds of fans at low voltage. In particular I have some Noctua fans which are not sensed correctly.

Rear Fan header at 5.55V (CPU idle with case lid off):
Scythe 80mm (DFS802512L from Ninja Mini HS): 1134 RPM
Sharkoon 80mm golf ball: 367 RPM
Noctua NF-R8 80mm: zero RPM reading (but it is spinning)

Rear Fan 2 (Aux): 11.95V
Scythe: 2063 RPM
Sharkoon: 778 RPM
Noctua: 1909 RPM

Has anyone seen this before?

It's not an issue with one particular Noctua fan -- I have several of them and they consistently give an RPM reading with the Aux header but not the Rear Fan header. I won't be changing the Noctua fans though -- they are really nice and quiet .

CPU fan = fan 1, Rearfan2/Aux= fan 2, Rear Fan = fan 4, so I guess the front fan will turn out to be fan 3.

It would be nice to know what all the temp readings are in the sensors output.