I have four case fans connected together through a fan hub or daisy chain. The main fan or hub is powered by a Molex connector from the PSU, so all the fans run at full speed constantly and are very loud. Each fan is described as having a 4-pin connector, and the case has a button for changing the RGB lighting, but it does not seem to control fan speed. Can I connect the group to a motherboard fan header to adjust their speed, and will the motherboard detect them correctly?
3 Answers
Check whether the 4-pin plugs are standard motherboard fan connectors or just proprietary connectors for the included hub. If the hub has a motherboard fan-control lead, connect that lead to a compatible 4-pin header and set the header to PWM mode in the BIOS. The Molex connection should then provide power while the motherboard controls the speed signal. If there is no control lead, the motherboard cannot regulate the fans through the Molex connection alone.
If the fans only have Molex power and there is no standard 3-pin or 4-pin motherboard connection from the hub, they cannot be speed-controlled through BIOS. Your practical options are replacing them with standard PWM fans, using a compatible fan controller, or installing an inline Molex fan-speed controller. Do not connect a proprietary 4-pin plug to a motherboard header just because it has four contacts, since the pinout may be different.
A Molex-to-4-pin adapter can sometimes let you connect the fans to a motherboard header, but it is important to check what the adapter actually connects. The motherboard header should receive the fan’s control and tachometer wires, not simply be overloaded with the full power draw. Four fans at 0.15 A each would be about 0.6 A, which is within the limit of many headers, but verify your motherboard manual and the hub wiring first.
If the adapter only supplies power and does not carry the PWM or tachometer wires, the fans will still run at full speed and the board will not be able to control them properly.
The fans are linked together, but only the main fan or hub has the Molex power connection. The case button changes the lighting, not the speed.