My colleague is using a Fujitsu Esprimo E900 (VFY:E0900PXG11NL) desktop PC that revs its fan every couple of minutes when a CPU core hits 70 degrees Celsius according to SpeedFan 4.51. Enabling "Automatic fan control" in SpeedFan doesn't help much (Is it still learning? Does not being able to show fan speeds affect it?).
The CPU is almost idle and there's no apparent dust in the case and another colleague says it's always revved. Is there a BIOS setting to control the fan speed?
Room temp is 25 C and desktop is clear. HDD temp is 40 C and average idle core temp is 60 C.
It appears that the fan can be controlled:
Special Features
Silent Fan – Independent temperature related processor
fan and system fan supervision and controlSystem Guard – View and adjust Silent Fan features
Unfortunately, Enhanced mode makes the front fan rattle (otherwise it would be the answer), Silent mode doesn't help, and Disabled makes it sound like a vacuum cleaner. I could ask the hardware guy about the thermal paste but all stock paste i've used lasted much longer than this and it seems all fans are entirely off until needed.
My colleague is fine with the revving on Auto, so i can't test SpeedFan again while BIOS fan control is disabled.
Best Answer
Enabling "Automatic fan control" in SpeedFan doesn't help much
If your motherboard is supported by SpeedFan then it should show the fan speed.
Normally SpeedFan is very good at auto detecting the temperature and fan speed sensors.
Unfortunately your motherboard does not seem to be in the list of motherboards that can change fan speed.
Image source Motherboards from FUJITSU/SIEMENS that can change fan speeds
Disclaimer
I am not affiliated with SpeedFan in any way, I am just an end user of the software.