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CPU Fan running at high speed for apparently no reason

Hi guys

My MB is KPGE-D16 and one of the CPU fans is very loud and it runs at very high speed (I think that the BIOS was showing ~4000RPM as opposite to ~1500RMP for the other fan

I removed the fan and I connected it to the other socket (this is a dual CPU MB) and the symptoms persisted. I took the fan to a store here in Canada to get an equivalent but I could not find one
this is the model: DF127015BU
I asked the in store service guy to test it and he connected the fan to one of its MB and the fan went on high speed again. He said the fan is OK but I can't say I totally agree. He told me that the MB can control the speed BUT I am running ESXi on this so not to many knobs at OS level to control the CPU fans

What should I do? What is wrong with my CPU fan?

thanks
U..U
Reply to UnicornU
5 answers Last reply Best Answer
More about cpu fan running high speed apparently reason
  1. I don't think that I have a thermal issue here, the fan goes crazy in the very second when it gets power.
    It was disconnected from the heat sink and tested on a different machine in the store as indicated above

    I can buy the fan only for 20CAD, shipping included, that is not an issue ...I was curious what is causing this
    Reply to UnicornU
  2. Best answer
    Ah. It's a pwm fan. Easy. Pwm is a pulse modulation. Basically the mobo sends the fan a signal to start/stop the motor to control the speeds. The fan itself is at a constant 12v, so the start/stops make the fan basically always in a state of trying to run full speed but never getting there. Inside the fan motor is a tiny pcb board that translates the signals and allows the voltage to be applied to the motor. In your fan, that pcb has a failed part, so the 'stop' side of the signal isn't responding. Which means there's no slowing the fan down from full 12v speeds. Which seems to be 4000rpm.

    So now your fan only works at 2 speeds, off (when the pc is off) or max (when it's on).

    There's better 70mm fans than that one. This fan is good, but the best is AcoustiFan DustPROOF 70mm, but it's expensive.
    https://www.coolerguys.com/products/evercool-70x25mm-high-speed-pwm-fan-ec7025sh12bp
    Reply to Karadjgne
  3. This sucks! I just ordered the wrong part
    Google could be a problem sometimes with their proxy resuls, they can't get you what you need but they give you something similar

    What would be an equivalent for DF127720BH ?
    Reply to UnicornU
  4. Kinda depends on exactly what the cpu cooler is, that's a specific design fan. Most fans are just square boxes. If you can use a plain fan, any 70mm should work, if it's specific, you might just need to use either your linked fan, or even scrap the whole cooler and use something else, which often times is easier, cheaper and runs cooler.
    Reply to Karadjgne
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