S9 Fan speed changes

[Ethero]

Hey there, I´ve got also the S9 in my office now and wondering about the changing fan speed. The temperature of the CPUs are all between 65° and 73°C and the fan has a minimum rpm of round about 4400 but then changes to 6700 for 20sec....then again to 4400 and again..again..again. It´s not a stable rpm from the fan. It changes every 20sec or so.

Is this usual that the fan is powering up and down the whole time?

The ASIC status is fine and I have also a good hashrate from 13.7 GH/s.

[VRobb]

That's what they do, yes.  Perfectly normal, Mine ON! 

[Ethero]

Alright..thanks!