I'm having the exact opposite problem. My fans keep coming on every few minutes.
Under Fan Control it is set to Auto (off/low/high) and the HDD Hibernation is set for 5 minutes. I have nothing talking to the NAS, so the HDD should be in hibernation, but looking at the System Status it keeps getting up to 45c and the fans come on high low until the system get back to 39c. A few minutes go by and the system temp creeps back up to 45c and it starts all over again.
Today is quite a cool day to the point I am going to put on some long trousers and shoes and socks. Any idea why the HDDs aren't spinning down, or why the system temp is going up so rapidly?
Can't find it now but before I found a spot that told me the HDD temps (4 x 3TB WD Red HDD and they ranged in the mid 30's).
The NAS box is sitting on the floor with nothing nearby it to create any heat or block air flow...
Edit:
Found the section that display the HDD temps.
Had gone up since I last saw it.
Drive 1 = 37c
Drive 2 = 40c
Drive 3 = 39c
Drive 4 = 38c