[SOLVED] Molex and 3 Pins

[bbyaga455]

I bought a chassis fan that has 3 pins goes to motherboard and a molex connector attached to the same cable next to the 3 pins .

My question is, do I need to plug them both or just one of them?

 

[jojesa]

I bought a chassis fan that has 3 pins goes to motherboard and a molex connector attached to the same cable next to the 3 pins .

My question is, do I need to plug them both or just one of them?

Just one at the time.
They provide both connectors just in case.

 

[bbyaga455]

How it'll know when to run and shut off? Like, it doesn't communicate with the motherboard.

 

[TerryLaze]

How it'll know when to run and shut off? Like, it doesn't communicate with the motherboard.

The molex is just a daisy chain, each plug always carries the same electricity as the other plug.
As long as there is no load (nothing plugged in) it's an open circuit, meaning that nothing happens and there is no electricity flow.
It only "runs" if you connect the neutral with the live line (by plugging something in)

 

[bbyaga455]

Let's say I chained all the fans one another, PSU has been plugged and switched to ON. While everything else in the PC were off.

All the molex will be off until I turned the motherboard on, right? It's not like running at all time.

 

[TerryLaze]

Yes, the mobo is the one turning on the power to the rest of the system.

 

[Paperdoc]

Those two connectors on the end of one fan cable are ALTERNATIVES. You can use ONE or the OTHER, but never both. Connecting both will have the fixed 12 VDC supply from the Molex connector forcing current backwards into the mobo header that is trying to slow the fan down by reducing its output voltage.