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I bought a case with a system fan already in place. It has the power connector but my motherboard has a system fan connector. My fan has a large connector and my mobod has a small one. This connector allows you to link with the cooling fan on the system case to lower the temp. What can I do?

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Two practical approaches work well here: keep the existing case fan but preserve motherboard sensing/control, or replace the fan with a native 3‑ or 4‑pin model that plugs straight into the board and is engineered for low noise. correctly pointed out powering from a PSU peripheral is electrically simple; the common compromise is to keep the fan powered by the PSU while still providing the motherboard with the tach (RPM) signal so automatic control and monitoring remain available (a concern raised by ).

How the headers behave matters. A 3‑pin header carries ground, +12V and a tachometer output; a 4‑pin adds a PWM input for finer speed control. Many motherboards can control 3‑pin fans by varying DC voltage (BIOS option: DC vs PWM mode), while true PWM control requires the 4th pin. Check the motherboard manual for header mode and the per‑header current limit before tying additional fans to a single header.

A safe method to preserve sensor/control while using PSU power:

  • Confirm pin/wire functions (do not assume colors — verify with the fan spec or a meter).
  • Power the fan’s +12V and ground from the PSU Molex, but leave the fan’s tach wire connected to the motherboard header so RPM is still reported.
  • Use proper crimps/solder and heat‑shrink; power must be off while wiring.
  • Boot and verify RPM in BIOS/hardware monitor and ensure the header isn’t being overloaded.

If quietness is the priority, replacing the fan is often the cleanest solution. Look for larger 120/140 mm fans with low RPM, fluid‑dynamic or magnetic bearings, low dBA per CFM, and rubber mounts. Brands with consistently quiet models include Noctua, be quiet!, Scythe and Corsair.

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Member Avatar for Member #23858

I found some info on this issue but Do you think the fan that came with the case would be good enough that I should get a 4 to 3 pin adapter and hook to my motherboard or do you think it would be best to get a new fan that already has 3pins? If so what is the quietest fan I can get? That is my biggest concern is quiet.

Member Avatar for alc6379

Why not just hook the 4-pin connector up to one of the 4-pin power connections that you'd use for a hard drive/ optical drive? That's what they're meant for.

All else fails, you could get a rheostat or a fan controller to control the speed of the fan.

Member Avatar for Member #23858

I know but then I lose the fan sensor. Not a big deal I know but...

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