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I m having a special system fan type in my computer which is very noisy (between 60 to 75 Db with vendor provided fans). But if nothing is plugged on it the computer refuse to run.
Here a what the plug looks like on the fan
From the computer s doc (I wasn t able to find the fan specific model) If pin 5 is linked to ground, the bmc will detect the fan as present, but this is not enough, so I tried to link pin 3 to pin 4 in order to fake rotation speed but the system still detects this as a faulting system fan (with message Lower Critical - going low - Asserted) and refuse to run in that case as if no fans where plugged.

What can be the proper way to fake the fan presence? Or what s the name of that type of connector so I can buy an adpter which would let me running a much more silent/acceptable fan for my neighbors?

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  • What OEM is your manufacture of your device (not the fan) you can edit your question to include this information
    – Ramhound
    Jan 19, 2021 at 1:13
  • I’d say without simulating an appropriate tachometer signal, this cannot work. Anything else will result in the firmware detecting the fan as stopped and thus failed.
    – Daniel B
    Jan 19, 2021 at 10:27
  • @DanielB I suppose tach is just a part of the fan with a magnet thus generating a signal at each revolution. That s why I thought pwm linked shall had worked because the pwm signal is tied to rotation speed. But looks like this is not in the way the system expect. Or yes, it can be a dynamo generating an analog signal.
    – user2284570
    Jan 19, 2021 at 10:37
  • @Ramhound currently it s full Intel, but I saw that fan plug on hp hardware 6 years ago.
    – user2284570
    Jan 19, 2021 at 10:39
  • No, PWM (pulse-width modulation) works differently. It is certainly tied to the speed (it is supposed to control it) but is a completely different kind of signal. Wikipedia has some great graphs illustrating it.
    – Daniel B
    Jan 19, 2021 at 10:44

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