Inspiron 5680 CPU cooling fan not recognized

Something wrong with this PWM fan?  If fan is not recognized but spins, sounds like it had power but no rotation speed feedback to motherboard.  If possible I would test heatsink fan in another pc to verify PWM works (that you did not get a faulty one), assuming the original stock cpu fan was recognized by 5680 and rotation speed was adjustable.

what about the original stock heat sink fan?  if you plug that one in the cpu fan header does your board read back fan speed in HWMonitor or speedfan app?

Thanks for the feedback - I wish I had another PC to test the PWM feedback on this fan, but unfortunately, I do not. I agree with your assessment that the fan is powered, but just isn't receiving any PWM feedback from the motherboard. 

Dell responded to my inquiry with "dell doesn't recommend third party upgrades, bye", which was super not helpful. 

I'm honestly wondering if anyone has upgraded the CPU fan on a 5680 motherboard successfully, or if it won't recognize any third party fans at all. Like I'm tempted to get a different CPU cooler, but I'm nervous that I will have the same issue. 

Neither HWMonitor nor SpeedFan can see or control CPU fans on Dell PCs.

Dell CPU fans are wired differently so BIOS can control their speed.  Non-Dell fan speeds typically can't be controlled...

In the old days of Dell giants they liked to use proprietary 5 pin special Dell fan connectors. In those cases it is probably correct that non Dell app is not able to access fan speed.  In current days more and more Dell cpu fans headers have moved to industry standard 4 pin PWM as verified by users report of easy smooth upgrade of Dell cpu fan to aftermarket model.  the 5680 uses standard 4 pin cpu fan header.  imo it should be accessible by non Dell app. https://www.dell.com/community/Inspiron-Desktops/Inspiron-5680-memory-question/td-p/5789919?lightbox-message-images-6033639=1804i87DFE8FB257FF9C0

PS evidence of other dell model cpu fan upgrade: https://www.dell.com/community/Desktops-General-Read-Only/XPS-8900-CPU-cooler-upgrade-much-quieter-and-cooler-operation/td-p/5105907

The HW engineering design in Dell has certainly had diverging directions: more industrial standard to fan and usb/front panel connector on one hand, more proprietary ATX connectors on the other. 

Dell whether using 3 pin or 4 pin or 5 pin header does not always use the same order on the pins as a standard fan.

Its bad advice to say that any standard fan works on any dell.

If you replace the dell fan with standard fan and it says fan not detected or other error its likely that the fan wires will need to be changed to be consistent with the dell output.

Look at the fan and determine where the BLUE wire is then the Red Wire then black then yellow or white wire.

Black = Ground

Blue = PWM

Yellow = Tach

Red = 12v

The common cooling fans used in computers use standardized connectors with two to four pins. The first two pins are always used to deliver power to the fan motor, while the rest can be optional, depending on fan design and type:

• Ground – common ground BLACK
• Vcc (Power) – nominally a +12 V RED supply, though it may be variable depending on fan type and desired fan rotation speed
• Sense (or tachometer)YELLOW output from fan – outputs a signal that pulses twice for each rotation of the fan as a pulse train, with the signal frequency proportional to the fan speed
• Control input – a  BLUE (PWM) input signal, used when the cooling fan assembly has an internal motor driver circuit. Fan assemblies with this control input provide the ability to adjust the rotational speed of the fan without changing the input voltage delivered to the cooling fan assembly. A variable rotation speed allows the cooling rate to be adjusted to meet demand, quietening the fan and saving energy when full speed is not required.
• https://www.handsontec.com/pdf_files/4_Wire_PWM_Spec.pdf

PINOUT