Fan Clicking and low Rpm's

falcon26 · Post by **falcon26** » Fri May 23, 2008 4:07 pm

I've got an 800 RPM scythe sflex fan that is totally quiet at 800 rpm's. But for some reason on my Dad's new Intel P35 motherboard it only spins at 400 rpms, and it clicks like crazy. I've checked the bios and their's no way to change the speed of the fan. Why would a motherboard run an 800 rpm fan at only 400 rpm's if I wasn't using any type of fan control in the bios or in windows for that matter...

widowmaker · Post by **widowmaker** » Fri May 23, 2008 5:18 pm

Insufficient airflow can result in reduced fan speed as the fan will need to work harder to pull or push air in or out of the case. The drag caused by insufficient airflow may be slowing the fan down. Imagine a fan pushing air, then imagine if you started blowing into the fan's intake side. This will cause the fan to spin faster, and is true vice versa. I don't think it could cause a 400rpm difference though unless your box is really sealed up tight. Try opening up the case and see if the fan speeds change.

Post by **NeilBlanchard** » Sat May 24, 2008 3:49 am

Hello,

It may be that the fan controller on the motherboard is a PWM, and this is causing the fan to click?

JaYp146 · Post by **JaYp146** » Sat May 24, 2008 5:29 am

NeilBlanchard wrote:Hello,

It may be that the fan controller on the motherboard is a PWM, and this is causing the fan to click?

Exactly what I was going to point out. This happened with one of my Yate Loon 120mm fans ... plugged it into a normal 3pin on my Nexus fan controller, problem solved (no more clicking).

falcon26 · Post by **falcon26** » Sat May 24, 2008 7:50 am

No this is in a regular 3 pin header on the motherboard. I'm wondering if the header isn't supplying 12V to the fan, its almost like the fan is running at 5V. Their is a 4 pin pwm header on the motherboard, 2 actually that I could try and see.

Felger Carbon · Post by **Felger Carbon** » Sat May 24, 2008 9:10 am

falcon26 wrote:No this is in a regular 3 pin header on the motherboard. I'm wondering if the header isn't supplying 12V to the fan, its almost like the fan is running at 5V. Their is a 4 pin pwm header on the motherboard, 2 actually that I could try and see.

Plug your 3-pin fan into one of the two 4-pin mobo headers. The clicking should go away and the fan should run near its default RPM. (A 4-pin PWM header provides +12V on pin 2, GND on pin 1, and the tach (RPM) signal on pin 3. A 3-pin fan will not connect to pin 4, which is the PWM control signal. The fan and mobo header are keyed so that you couldn't connect the fan wrongly even if you tried.)

falcon26 · Post by **falcon26** » Sat May 24, 2008 9:21 am

I just plugged it into the 4 pin pwm header and now its fine and running at a full 800 rpm's and still dead quiet

Thanks.