Z77: Fans (3pin) won't start up unless connected to molex

Hi,
I've been building a quite nice system within a coolermaster cm690 ii advanced.
I've connected the 2 chassis fans (rear & top) to the correct places on the mobo (asus p8z77-v lx) but they don't fire up when powering on the pc.

Is it possible that they just start when the heat requires it?
I'm just confused by the thought that they wouldn't even start when booting up the pc.
(And they haven't fired up yet, altough I haven't been able to get my system really hot despite some heavy usage)

Connected to the molex adapters they run just fine, but arent controllable though...

Thanks for any info!
5 answers Last reply
More about fans 3pin start connected molex
  1. Do they work when you plug them into another fan connection on the motherboard? I hope you didn't plug a case fan into the CPU_fan connector.
  2. It doesn't matter which 3 or 4 pin headers on the board you plug the 3 pin fans into. They should come on as soon as you start the system. If not, there's something wrong with the board.
  3. I've just plugged the rear fan into the power one for testing (I've left the cpu one untouched), and the fan started up fine.

    Since I don't have anymore fan connections than cpu, cha1 & 2 and power, I can't test more out. I've checked in the bios and the two cha fans arent being monitored and arent running even though plugged in correctly.

    What to do? :(
  4. Just as clutchc said, fans should start up when the computer starts up. Can you take some pictures so we can see how you setup your motherboard?
  5. You should be able to set them to 100% in the hardware monitor. if they don't come on, the fans are known to work, and they aren't one of those setups that plug into molex and only have the yellow rpm wire to the 3 pin then the board is deffective. I'd try a BIOS update first, but the board probably is going to need rmaed
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