No, you shouldn't exceed the voltage rating of a fan header.
No, you shouldn't exceed the voltage rating of a fan header.
I’m not very familiar with electricity, but I noticed the voltage readings are changing. The fans are drawing 0.30 amps while the motherboard headers show 1 amp. Those Corsair AF120 fans seem to be operating at around 13.7 volts, which might explain the difference. It’s possible the specs have been updated or there’s a misunderstanding. You should probably double-check the manufacturer’s guidelines before using them.
Yep, even if it was 0.3A @ 13.7V you could use it. You probably aren't going crazy, if I had to guess what happened: the listing probably had only the upper voltage limit stated, like so: ^ https://www.corsair.com/us/en/Categories...tech-specs That is the upper limit, go higher than that and the fan will fail, for all intents and purposes this is a 12V fan. Anyhow looking at the specs for AF120: ^ https://www.corsair.com/us/en/Categories...tech-specs So these are *voltage controlled fans aka DC mode , 7-12V and drawing 0.3A per fan. If the mobo header can provide 1 AMP you can use up to 3 fans on the same header (using a splitter cable, 3x0.3A=0.9A). Though I personally would either use 2 mobo headers, so that 2 fans are connected to 1st header (total of 0.6A) and the 3rd fan connected to 2nd header, or I would use a fan hub.... which adds cost (unless you already have a fan hub, which can do voltage regulation). * I bolded the voltage controlled because you can clearly see it says PWM Control - NO for the AF120. PWM = Pulse Width Modulation, fancy term for switching something on/off (usually) quickly to regulate the intensity (fan speed or brightness of an LED etc.). For these fans to work properly your mobo header needs to be capable of doing the voltage control (change fan speed by adjusting the voltage), most new mobos can do both on most of the headers, for example MSI MAG B550M Mortar: As you can see PUMP_FAN1 can provide whopping 3A, but it is PWM only, so you can't plug in your fans into that header. Also worth noting is that you will most likely need to go into BIOS settings and manually set the fans to DC mode, since Auto detection usually only works on the CPU fan header (which will hopefully be occupied by your CPU fan, and not case fans heh). Let's say this is your mobo, I would either connect Fan1 & Fan2 to the SYS_FAN1 header, Fan3 I would connect to SYS_FAN2 or I would connect each fan to a different header (if the fan cable can reach that far and I don't have a splitter cable on me). Finally I would set the fan curves to match each other, they don't have to match but it would be weird to me if they were spinning at different speeds. Anyhow, please check the manual of your mobo for which headers can do voltage control.
Thanks for the details. Just confirming a few points. My motherboard is the Asus ROG Strix B550-F gaming, and all headers share the same maximum current (1A) and power (12W), including CPU_OPT and AIO_PUMP. The headers are Q-Fan Controlled except for the AIO_PUMP. It does have Full-Speed fans. Regarding your question about fan splitters: using a 3-pin plug is acceptable since most splitters come with 4 pins, so it should work fine.
It's best to avoid running a fan at full speed when the PC is idle. You can adjust case fan settings with cpu-opt. For Asus TUF models, set your AF120 fans to DC mode and enable the "optimize all" feature to determine their minimum speeds. The 4th pin is used for PWM control; voltage-controlled fans don't rely on it. It's perfectly okay.