Hardware Monitor, if Aux is being read from an unassigned input, then just ignore it. In SpeedFan, Aux can simply be disabled, and therefore ignored. My Aux temperature is currently 17c, which isn't possible, since ambient is 25c. I've seen it vary from -19c to 127c, which means it's an unassigned input from the super I/O (Input/Output) chip on the motherboard. It's a common anomoly.