• Our team is working to address issues posting quotes or media to the forums. Please bear with us as we get this sorted out.

Question NHD15 fans stop spinning momentarily


Nov 22, 2015
So I bought the D15 for my system set it up, saw a pretty decent decrease in temps overall and under load, but I noticed the outer fan that I could see, would slow down sometimes. I chalked it up to the system controlling it, because I didn't adjust any of the CPU fan settings and instead left those up to the system.
Booted from sleep this morning, and I noticed the fan would spin and stop, spin and stop, it'd spin for a good couple seconds, then stop. So I checked the interior fan as well that's in the middle of the cooler and realized that was doing the same thing, they were operating in unison.

So is this a default setting, is this normal? Or is there something wrong with the fans.

mobo is a b450-f gaming ii
cpu is a 2600x.


Apr 7, 2019
The Noctua NH-D15 CPU Air cooler has 2 fans. You can opt to install either 1 fan or 2 fans onto the CPU cooler. I have it too but only installed 1 fan and still decent enough to cool my CPU temps. I couldn't install the 2nd fan because RAM was in the way so I plan for it to be the replacement fan when the 1st one breaks down (and they last for a very long time).

My guess is that the fan settings in your BIOS for the CPU Fan needs to be changed to PWM mode and not VDC, otherwise I would test out those fans by connecting it to another system and see if the behavior is replicated. If the behavior is the same, then the problem is with the fans.
Check your bios fan settings.
A fan needs sufficient voltage to start(5v), that would be likely at 500 rpm.
Noctua supplies a splitter to connect both fans to the cpu fan header so they can be both controlled in the same manner.
The fans are very quiet, they are all but inaudible up to 900 rpm.
You can start them higher.