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I need to replace a 2-pin fan on my PSU unit. The fan is 40x40x20, DC12V, 0.15A. I am replacing the fan because the noise is unbearable, >75dB right next to it. fan

Can I simply buy a 3-pin fan and cut off the 3rd cable? I was unable to find any 2-pin cable in stores around me and I expect there will be even less choice if I want a silent fan.

What happens if the new 3-pin fan is not rated as 12V fan, but 5V? Do I just add a resistor to the positive cable?

Another issue is that the connector won't fit and I’ll need to use the existing connector or buy an 3-to-2-pin adapter, if I can find one. fan connector

Thanks for the help.

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    \$\begingroup\$ I strongly advise you to replace the fan with exactly the same model. Delta electronics is a reputable brand so I'd stick with that. Of course you want a more silent fan but what if such a silent fan provides less airflow causing your supply to overheat, possibly suffer damage or even catch fire? Are you willing to take that risk? Also go and study what 3 pins fans need 3 pins for and why 5 V isn't an issue. As mentioned in an answer a 12 V fan with 3 pins can be used: use the red and black wires only. \$\endgroup\$ – Bimpelrekkie Sep 24 '20 at 14:09
  • \$\begingroup\$ Thanks. I am trying to find the information on how much RPM and airflow does my current fan have. I contacted the manufacturer because I was unable to find exactly the same model online. I did find EFB0412HD but not EFB0412HDD. I will try to replace it with a same fan first because I noticed that these fans are rated at around 30 dB. I really don’t understand how can a new product (NVR) that this PSU was built -in produce that much noise. I repeated the measurement and even 2 feet away it is still over 50 dB and at the time this was the only fan running. \$\endgroup\$ – miran80 Sep 24 '20 at 15:14
  • \$\begingroup\$ One more thing: All fans have a limited lifetime. The fan I have now has 2 cables only, no 3rd cable to report back the speed. How will controller detect fan failure and shut down the PSU? There must be a temperature sensor somewhere or the product is already a fire hazard. A fan dying is more a question of when, not if. The software only reports CPU temperatures, and CPU has own passive heatsink. There is no reporting of the PSU temperature but I have a laser thermometer I can use to measure it if I knew what part is the critical in terms of overheating. PSU image: prntscr.com/un65et \$\endgroup\$ – miran80 Sep 24 '20 at 15:27
  • \$\begingroup\$ Found a specs sheet for EFB0412HD (not HDD): delta-fan.com/Download/Spec/EFB0412HD.pdf If they are anything alike, I would need a fan with min 7600 RPM and 0.242 m3/min air flow. Sadly the "silent" Noctua NF-A4x20 FLX only has 5000 RPM and 0.156 m3/min air flow so it is not really an option anymore. \$\endgroup\$ – miran80 Sep 24 '20 at 15:44
  • \$\begingroup\$ A fan dying is more a question of when, not if. I don't think it is that bad but it makes for a better design if you take possible failure into account and for example, implement an overheating protection. That costs money though so don't rely on that being present. The main issue with a fan this size is that it is small. For good airflow without much noise, you need a large fan. \$\endgroup\$ – Bimpelrekkie Sep 24 '20 at 19:30
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Usually the 3rd pin is the "tachometer" output so that the fan's speed can be read by whatever is controlling it.

So in the case of a 2 pin 12V fan, you need only to connect the power leads properly and leave off the tach output since nothing in your PSU is expecting it.

As far as the connector, it's often simplest to cut the wires off the old fan and simply splice the wires onto the new fans leads. Finding such connectors by themselves can be tricky.

Do not substitute a 5V fan for a 12V fan. While it may run for a while, the fan will likely overspeed, overheat, and likely fail in a relatively short period of time.

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    \$\begingroup\$ Yes, and just by a 12V fan not a 5V when you need 12V... \$\endgroup\$ – schnedan Sep 24 '20 at 14:07
  • \$\begingroup\$ I will try with a same model fan first, 12V and hopefully it won’t be as noisy as the one the product shipped in. If I could match voltage, RPM and air flow, I would however consider a Noctua fan, provided that they have a 2 pin connector or adapter to make it easer to attach. \$\endgroup\$ – miran80 Sep 24 '20 at 15:17

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