You mentioned, "auto fan speed", so that suggests it would kick-in when needed. Unless the setup provides a basic level to act upon, it's all left to the pgm. to select. Of course, if possible gets the latest update it may also provide more user set levels -OR- visit the support website and see what has provided as an answer or query there.
Currently I have my HD 6950 set with auto fan speed. When I run furmark I get temps around 85C and a fan speed around 35%. I tried running it at 50% fan speed and it was much cooler (I know 85 is okay but I would prefer a lower temp). The only problem is I don't want the fan running at 50% when idle. Is there any way to get the fan to spin around 50% only when necessary and revert to auto when idle?