Question about case fans?

As you all probably know by now I just put together a new computer, its my first time and I’m still learning.

This time my question is about case fans, when I originally hooked up my case fans (120mm rear and 80mm front) I hooked them to my Asus P5B-E motherboard, then after the OS was installed I installed my Asus software to monitor and tweak things like fans. After I did I noticed that my 120mm exhaust fan was running below the allotted threshold (800rpm) and my 80mm didn’t register at all. I set the fans for performance in the Asus program but nothing changed, so I unhooked them from the mobo and connected them directly to the psu. They seemed to run faster although I have no idea how much faster since they cant be monitored.

Is there something I can do to get these fans to work properly on my mobo, or is it ok to have them hooked directly to my psu?

Thanks in advance for any input!

EDIT: Here’s a link to my case-

The fans that aren’t registering probably don’t report their speed. I have one fan (Panaflo) that’s like this. If that’s the case and you want to monitor the speeds, you’ll need to get new fans.

Just thinking aloud, but isn’t the third wire on a fan the ‘monitoring’ wire? So if it has three wires it will report its speed. Then, if it’s slowing down it’s the BIOS telling it to?

So, if they’re all 3-wire fans, and they’re connected to the MB then it’s a BIOS issue. Check the BIOS for a ‘fan control’ setting would be my guess. From ‘auto’ to ‘full-boar’.

Yup, look in the bios and tell it to cut the crap. I had the same problem with my Asus so I disabled their MB controls in the bios. I use a custom controller that I built and I use the Asus MB monitor too.

Edit: Typo

What FIDGAF said - but!

Are the slower speed causing you any problems? Instability? Too high temperature?

I don’t overclock but usually run pretty fast systems - I have yet to need a case fan at all, so perhaps your 2 are fine just running at the slower (and less noisy) speed?!
Unless you’re an overclocking fiend or live without AC in the middle of Texas.

I messed around with the Bios but still couldn’t get the fans to speed up, they seem to run faster hooked directly to my psu, so for now I think I’ll leave them hooked up that way till I can get a custom fan controller.


I do plan on OC when I break in my new HSF. I can’t stand a hot machine, but I suppose I should stop checking my temps all the time. I’m never happy, if I get my temps down 5*C then I think why can’t I get it down a little bit more, its a vicious cycle!

The yellow wire on the fan is the sensor wire. There’s usually a heat sensor that governs the fan speed\voltage going to the fan. If the sensor doesn’t see a need to increase the speed of the fan, it won’t. Perhaps it already IS running at the correct speed and there’s no need for the fans to be at max RPM.

What are your temperatures reading?

Generally I prefer to run the fans directly off the molex connectors because motherboard sensors usually don’t know wtf they’re doing, and neither do power supply “fan only” molexes (which base speed on the temperature inside the PSU).