I jumped right to a BIOS reset.  Unfortunately had the same issue right after.  While setting up my custom settings, I noticed that it reverted the thermal settings again.  The solution is to change the Performance profile.  When it is on Performance or when CPU is otherwise set to Maximum Performance, it forced iDRAC to run the fans at max in the thermal options.
I have a Dell R620.  Every time it boots, it resets the iDRAC settings to default - including the thermal settings.  Because of this, the fans run at 100% speed.  I have updated the BIOS to 2.9.0 and iDRAC to 2.65.65.65, but the issue persists.  How can I correct this issue?
iDRAC settings not saving