"Fan not working" alert when replaced fan

Hi all,

I’ve replaced factory fan on my WD My Cloud EX2 Ultra with Noctua NF-A4x10 FLX fan.

All works great, fan is very very silent, temperature keeps as before (if not better) but, what happens now, is that time to time (every other day or so) I am getting “Fan not working” error notification.

I suspect there is some kind of monitoring for the fan RPM, in case of Noctua fan the RPM is about 2200 which might be lower than the original.

The alert seems to be triggered right after NAS wakes up from sleep.

System Test also returns all good with fan:

Anybody knows how the fan status monitoring is being implemented on OS5?

Would be very grateful.


Some systems may need a 4 wire fan
No idea if a EX NAS does but may be a place to look

1 Black GND (0V)
2 Yellow +12V
3 Green Sense/Tach
4 Blue Control/PWM

Hi. Thank you for the reply. Wiring is definitely correct (the same). Even system reports all good. Seems on the NAS wale up something is different and OS thinks fan is broken, but is not…

One item to check with a new fan is the default start up speed.
Some will not start up at low RPM setting and can stall .
They can start to spin up and start working if they warm up or get bumped.

I have most of my fan curves set to 30 percent at low speed.

Others on the Forum have shown how to change the fan temperature - RPM curve settings but making the code change stick is always a problem.

Indeed, that might be different. Noctua fans are much more efficient, so RPM is much lower than any other “noname” fans.
What I am looking for is to find out where/what script/daemon is checking “fan condition” and reports alerts according to that so I can update it to suit Noctua…