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I need to replace a pc-fan 2 pin(80X80X25mm). The only details it has are:12V/0.14A.(no RPM/CFM details). Will those details(voltage/current)enough and i can pick any 80X80X25mm 2-pin pc fan which has the 12V/0.14A value or it might be a case,that the rpm/cfm of the replacement,will be different in spite of the identical voltage/current?


closed as off-topic by Scott Seidman, brhans, Chris Stratton, Voltage Spike, duskwuff Feb 20 at 1:02

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  • \$\begingroup\$ Yes, it will be different per (type of) fan. It depends e.g. on the bearings, torque constant, speed constant and such parameters. Despite the same power input, the different fan parameters give different efficiency and so different output power (which is torque times angular velocity, the latter being related to RPM. \$\endgroup\$ – Huisman Feb 19 at 18:06
  • \$\begingroup\$ Is the fan on a heat sink or attached to the case? Fans for the former tend to have their blade geometries optimised for a higher back-pressure (to push the air through the obstruction of the heat sink), and the latter for more airflow. \$\endgroup\$ – Andrew Morton Feb 19 at 20:07
  • \$\begingroup\$ Is this for a PC or other device? Have you made changes to airflow(aftermarket filters, etc), do you use the device only in clean environments (Negligible dust inside when you opened it to check it)? What is your budget? Is a better fan acceptable or do you specifically want to match it? If it's a computer you're using, what are your PSU, processor, motherboard and graphics card, and how many other fans and of what ratings are you using? A broken fan is an opportunity to improve stability/reliability/performance. You can also likely use almost any generic 80mm fan if you're on a budget. \$\endgroup\$ – K H Feb 19 at 21:38
  • \$\begingroup\$ Oh, and what are the brand and serial number (picture of sticker) of the original fan? \$\endgroup\$ – K H Feb 19 at 21:41

The first thing is to match the size, because if you don't modification to the chassis will be necessary.

Then you'll probably want to match the connector (which will also match the voltage)

The fan needs as much current as the channel it sources current from on the power supply (example, if the fan uses a molex connector with 12V @ 0.3A then the power supply on that channel needs to be able to source 0.3A. Generally this isn't a problem since most power supply channels can source 2 Amps or more)

If you get a fan that has the same voltage, and less or equal current you can't go wrong.

  • \$\begingroup\$ So,are the main factors of the motor rpm/cfm related in most to the current and the voltage?(besides,maybe,a small rpm difference as Huisman mentioned)like if the current will be higher the rpm will be higher?(just for understanding,i am not going to pick an higher current pc fan)Also,The old pc fan has 4 poles,if a pc fan motor will have the same size,voltage and current but with more poles,will it change the rpm? \$\endgroup\$ – xchcui Feb 19 at 19:33
  • \$\begingroup\$ If you need the same air throughput then make sure the CFM is equal to or greater than. \$\endgroup\$ – Voltage Spike Feb 19 at 19:43
  • \$\begingroup\$ is equal to or greater than...? CFM was unknown... :) \$\endgroup\$ – Huisman Feb 19 at 20:22

There's some correlation between the current drawn and the airflow a fan produces, no matter the other factors which affect this -- RPM, blade count, depth and pitch. Pick one of a similar or slightly higher current, but compare the blade details for similarity if possible. A higher current is unlikely to be an issue with the supply, though a fan that runs at a higher RPM will be noisier if the original one was a low speed device.

For a system that is going to get a lot of hours, pick one that has a rated life that is at least 40,000 hours (reputable companies put this in their datasheets), this probably means it'll have ball bearings rather than sleeve bearings. I replaced one a couple of days ago that had about 18 years of service before it started squealing, the bearings were bone dry and beginning to shed metal that was coating the magnet inside the rotor.


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