One of the front case fans making noises, stopping and restarting from time to time

TudorF · February 15, 2022

I have two frontside Arctic case fans (120mm P12 PWM PST A-RGB 0dB Black) I installed last year. Worked without any issues so far.

Suddenly today, the one on the bottom started making noises and running at irregular speed.

Opened the case, it kept accelerating and decelerating in a way that was out of synch with the fan above. They're both chained and connected to the mobo with one connector for power and one for LED control.

I tried shutting down only the bottom fan, but since they're chained, both get stopped. After a while it started making even louder noises like this:

I went in the BIOS and turned it down manually. Opened the case, unscrewed the fans and took a look at them.

Nothing looked wrong mechanically, but then they're probably very sensitive to any slight warping or dislocation from the axis.

Every few weeks I have been using a vacuum cleaner to pull out the dust from the front case grill. I was thinking that maybe this might have drawn the blades off center or something.

I changed their positions, so I placed the one on the bottom (which makes these noises) on the top spot and the top one on the bottom.

Cleaned up the blades a bit with some ethanol then reconnected to the mobo.

Started in BIOS, set them at about 750 RMP at 35°C temperature, a bit lower than before (used to be around 1000 RPM).

Now they work fine.

What could have caused this, could it be a controller issue or some mechanical issue? Since they're both chained, I suppose they get the same signal in the same way from the mobo.

So that leaves only some hidden mechanical issue. Anyone seen this kind of issue with case fans?

suedseefrucht · February 15, 2022

22 minutes ago, TudorF said:

I changed their positions, so I placed the one on the bottom (which makes these noises) on the top spot and the top one on the bottom.

22 minutes ago, TudorF said:

Now they work fine.

22 minutes ago, TudorF said:

What could have caused this

It doesn't look like there would be any cables in the way of the fan, so I think it's been a bad electrical connection. When connected, it ran fast and when not connected it slowed down and the continuous on and off caused the noise.
Now, that they are connected by other connectors, because you swapped the fans, it works fine again.

(Yes, PWM is basically continuous on and off, but maybe it was not the signal, but the supply voltage.)

Ralfi · February 15, 2022

54 minutes ago, TudorF said:

Every few weeks I have been using a vacuum cleaner to pull out the dust from the front case grill. I was thinking that maybe this might have drawn the blades off center or something.

If you did this with the vacuum cleaner on high speed, it could damage the fans. Just make sure it’s on low & stop if you see the fans spinning as you use the vacuum.

57 minutes ago, TudorF said:

Started in BIOS, set them at about 750 RMP at 35°C temperature, a bit lower than before (used to be around 1000 RPM).

Now they work fine.

& what happens if you set them to 1000RPM again? Best to test them to see if the issue’s gone.