ALL fans (CPU, GPU, PSU) suddenly too slow

Hi, I'm having the problem that literally from one day to the next, all of my PC's fans are malfunctioning.

The PC was working fine with no problems until recently. I turned it of, turned it on again the next day an immediately heard a "crunching" noise from inside the case.

Of course I turned it of immediately, opened the case and checked for any damage, obstruction of the likes. I found nothing at first glance, so I left the case open, turned it on again and observed.

While the crunching noise did not come back, I noticed the following things:
First: The CPU fan did not rotate, but it seemed to try: Sometimes it moved a bit and then stopped again. It never made a full rotation.
Second: One of the two GPU fans seemed to slow down sometimes and then speed up again. The other GPU fan was rotating continuously as it should.
Third: Noises I would describe as clickering came from the PSU.
On a software side, I noticed no malfunctions of any kind. The PC booted up normally. From the desktop (Win7) I watched the CPU and GPU speed for some time, felt the heat sinks and everything seemed OK temperature-wise. Interestingly, the CPU fan started rotating after some time, although very slowly and definitely slower than usual.

I rebooted the PC and deactivated Smartfan in the BIOS. Now the CPU fan was rotating at high speed, so it does not seem to be damaged mechanically. The clickering noise from the PSU remained.

Rebooted and went to BIOS again, activated "Alarm if PSU fan stands still". After leaving the BIOS, the alarm sounded up immediately, so the PSU fan seems to be malfunctioning as well. When I deactivated the PSU fan alarm and activated Smartfan and "Alarm if CPU fan stands still", the CPU fan stopped as it did before, and as expected I heard an alarm as well.

In summary, it seems that all of the PCs fans, but at least the CPU and PSU fans are malfunctioning. The CPU fan does not seem to be damaged mechanically. I did not notice any other malfunctions aside from the fans.

Does anyone have an idea what could be broken? The mainboard? The PSU? The heat sensors? Something else?

My system's components:
OS: Windows 7 Professional 32bit
Mainboard: Gigabyte 870A-UD3
CPU fan: Scythe Mugen 2 Rev. B
GPU fan: MSI Twin Frozr II (came with the GPU and was already built in)
PSU: Cougar SE 400

Thanks for any help!
2 answers Last reply
More about fans suddenly slow
  1. Sounds like you popped a component in the +12V area of your power supply, which typically means you killed that rail, and its completely unusable. However in your case it didn't completely fail.

    I would recommend, turning off your pc, taking out the power supply, jumpering it to allow it to run disconnected then check its outputs, another option is discharging the capacitors then opening it up (be sure you discharge the capacitors otherwise you risk giving yourself an uncomfortable shock) to see if things are indeed crispifried in there. (OPENING YOUR PSU WILL VOID THE WARRANTY). You could just also swap in a new psu and see if that solves it using the process elimination, The other major possibility though not as based on symptoms is the fan controller, but in this case I am about 85% sure based on what is described as a burnt power rail.
  2. Maxor1, thanks for your reply! Basically what you explained fits witch what I thought might be wrong, i.e. something with the PSU. I didn't know there is a separate 12V area that could be broken while the rest is still functional, but with that in mind your hypothesis makes a lot of sense.

    Since my other, older PSUs are not compatible with the PC, I had to order a new one which I'm gonna try as soon as it arrives.

    The warranty of my supposedly broken Cougar SE400 is still valid, so I will unfortunately not be able to open it and tinker around with it ;) :(

    I'll definitely report if the new PSU fixes the problem, and if it does, claim the warranty.
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