Are you sure that you got the PWM fan? If so, it is now running at 100% fixed fan speed, since the R909 only outputs a 3-pin DC fan signal and Noctua PWM fans default to 100% fan speed if they get a (any) 3-pin DC fan signal.
Yes, I confirm I bought the PWM model. The PWM part isn't important for the R909, but it is the 80mm Noctua model that has the most airflow.
