CPU fan speed low?

Jgpassage

Jgpassage

New Member
Today I noticed my CPU cooling fan wasn't as loud as usual. Interestingly enough my Coretemp readings were higher than usual (60 degrees C and climbing) I went into BIOS and noticed fan speed was at 1229 RPM. Fan speed was usually over 4000 RPM. I also noticed BIOS wont let me change fan speed, no matter what I try. I tried disabling Q-FAN, saved changes and exited BIOS, no changes. I dont understand whats going on. Cant find anything after hours of Google research.

Can you help, please? Never had this problem before.

ASUS M4A785-M motherboard. AMD Phenom 9550



 
Last edited:
Are you talking idle or under load? Really at idle it should not be anywhere near 4000 RPM. Sounds like you got some problem going on other then fan speed. How long has it been since you cleaned off the CPU and cooler and reapplied compound?
 
The fan is a 80 mm fan, they usually spin faster, don't they? It was hitting 70 degrees C last night (critical temps) under idle just in BIOS. The fan speed was still sitting at 1229 RPM. It should be speeding up drastically to lower temperature, whether or not the CPU is seated correctly. The CPU was cleaned and reapplied compound 3 weeks ago.

I mean I've seen the BIOS speed the fan up automatically to 3000 RPM to counter temperature before, I thought that was normal.

Ok I got another fan, a 120 MM fan (it's only 3 pin, not 4 pin though) and plugged it in. It's spinning much faster (2528 RPM) and temperatures are much cooler 32 degrees C under load. I can assume the 80MM fan is broken? Just never had this happen before.





Ok now that I have the 120 MM fan working, what voltage should the fan be set at in BIOS?

Ok so temps are now at 28 degrees C with loads. MUCH better.

I'm assuming the PWM (4th pin) controller on the motherboard has malfunctioned? The PWM interface in the BIOS has disappeared.

Ok now I know that the motherboard doesn't allow manual speed changes using 3 pins (I guess? It doesn't specify)
 
Last edited:
I found after checking manual again that this motherboard does NOT change CPU fan speeds at all using 3 pin fans, including voltage changes. It does, however with 4 pin fans. So either the 80 mm fan has malfunctioned or the PWN controller on the motherboard has malfunctioned.

Either way 3 pin 120 mm fan is rigged on top of cooler and all is well. Cooler than ever before, actually. Kind of cool ;)

I guess to anyone that ever has a CPU fan problem, since I couldn't find help externally:

-Check to see how many pins CPU fan has

-Check motherboard manual to see if BIOS allows changes in CPU fan speed

-3 pins= 12V voltage control; 4 pins= PWN (Pulse-width modulation) enabling Q-Fan (Asus BIOS "smart fan")

-If you have 3 pins and can't find any voltage control for fan, you CANNOT control fan speeds with 3 pins, fan runs full speed at all times

Hope this helps others. Thank you.
 
You must log in or register to reply here.
Back
Top