According to this posting, my Linux-computer ‘Phoenix’, which is also my Web-server, once had a failed case-fan, and I had replaced it with a new one.
I knew that the old one had failed, both because my desktop widget showed it as only spinning intermittently, and because when I inspected it, with the tower-case open, I could sense with my hand, that the old fan had increased resistance to being turned. I assumed some sort of bearing failure.
The new case-fan did spin at full speed correctly, for some time.
But in recent days, I find that the new case-fan has failed again. I really have no explanation for this, but my widget now shows its RPMs doing the same thing they were doing, for the old case-fan, sometimes spinning, and sometimes stalled.
Now, I could undertake simply to replace it again, with a 3rd fan. But since the first repair did not work, I have no reason to assume that replacing the case-fan again would work. And so I am left pondering, what I should do.
(Edit 05/20/2017 : )
I think that the big illusion in this subject could be, that just because my widget tells me that the fan has stopped spinning again, it must be for the same reason.
Alternatively, it could be the case that if I was to open up the tower and inspect this new fan, I might find that it spins easily to my fingers – unlike how it was with the old one.
Exactly as I am writing this, that fan is indicated as spinning again, at low RPMs of 1000.
Simply having to open up the tower would imply downtime for my site, and unless I both know with greater certainty that there is a problem, and how to fix it quickly, I’m unlikely to undertake doing so.
The problem with the newer fan might be, that the motherboard is allowing it to spin at lower RPMs, just because it is not very hot inside the tower (according to the same widget), and that when given little juice to run on, or when given very brief pulses of PWM-controlled voltage, the fan sometimes just fails to spin at all.
(Edit 05/21/2017 : )
I seem to have a second confirmation of this idea today, because my widget actually tells me the new fan is spinning around 600-800 RPM – steadily and with stability, while the temperatures inside the tower are cooler than usual.
The old case-fan never went that low in its RPMs, which suggests that when the temperatures inside the tower are indicated to be cool and friendly, the motherboard sends very short PWM-pulses of power to the fan, due to which the fan should spin at very low RPMs, that also imply very low torque, since according to my last test, it spins very easily and loosely.
So it can happen, that the motherboard might sometimes just not send the fan enough torque, to be spinning at all.