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My case fan from antec has a 4 pin molex. I want to connect it to the mobod to be able to control the speed with the mobod controller but need a 3 pin. Is there a way to do this?

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Dani AI

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This thread mixes two different connectors and control methods, which is the root of the confusion. The large 4‑pin Molex from the PSU is a power plug (yellow = +12V, red = +5V, two blacks = ground). Motherboard fan headers are the small 3‑ or 4‑pin connectors: they supply power and a tach (RPM) sense, and the 4th pin on PWM headers is a separate control signal. Confirm the actual pinout on your fan and on the motherboard manual before touching anything.

Power source determines control. A fan powered directly from the PSU Molex will normally run at full 12V; the motherboard cannot reduce its speed unless an active adapter (one that switches the 12V under control of the board’s PWM or sense line) is used. Passive Molex-to-fan adapters usually only give power (and may omit the tach lead), so you lose motherboard speed control and in some builds you also lose RPM reporting.

A quick safety checklist: read the fan’s spec label for current/amp draw, then check the motherboard header rating in the manual. If the fan draws more than the header is rated, don’t power it from the header — use a powered adapter or external controller. If you ever splice or rewire, verify polarity with a multimeter and preserve the tach wire if you want RPM monitoring; a miswired connector can damage the header.

Practical choices remain: use a fan with the matching 3/4‑pin connector for the motherboard header, use a proper active adapter/harness that preserves RPM and supports PWM switching, or use a dedicated fan controller. ’s DIY approach can work but requires care; ’s warning about current is important; and ’s pointer to search for adapters is fine — just pick one that matches your control goals and the safety points above.

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Member Avatar for ^^!

I beleive there would be some sort of an adapter but im noy entirely sure... google for Molex Adpaters

Member Avatar for nizzy1115

yes there are, and you can buy them for about $5. Honestly though, if you have an old 3 pin fan just cut the wires cut the wires on your 4 pin fan and connect the 4 pin fan to the 3 pin adapter. It works like a charm (ive done this about a dozen times). Or if you want to spend money you are best off buying a cheapo fan off newegg for about $5 that has an adapter with it (many do).

Member Avatar for alc6379

Be VERY careful, though-- sometimes you can pull too much amperage through the fan, and ruin your motherboard because you sent too many amps through it.

If you've got a 4-pin fan, just buy a fan controller, and control the speed manually. They're not all that expensive, and you can usually control more than one fan with them. I've got one in a 5.25" bay that controls 4 fans from one spot.

Member Avatar for Member #23858

I just bought a new 3 pin fan and solved the problem much cheaper. All done.

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