CPU Fan Trouble...Help!!

[n8thegr8]

Hi all,

Just completed a build today. Giant red flag when i turned it on: the CPU fan would pitter every few seconds, but never spun up. I shut off the computer immediately and grabbed a big house fan, and started troubleshooting.

I'm using an aftermarket heatsink, so my first troubleshoot was to attach the stock intel heatsink to the cpu fan pins on the mobo, same result. It appears the 4-pin power socket on the mobo is dead.

Right now I'm running the cpu fan through one of the system fan power sockets on the motherboard, and it works alright.

My concern: the fan is only running at 400-600rpm. The AC Freezer Pro 7 is rated at 900-2500rpm. Theres barely any airflow coming out the back i can feel with my hand, certainly mucch less than I felt with my Athlon64 in my older computer.

The 3 case fans work fine, 1 of them I have connected to the motherboard which reads it at 1200 rpm.

Should I be worried about the low cpu rpm? The temperatures are pretty good so far, thats what counts (22C at boot, 27C idle), though I was planning on overclocking. Is it safe to plug in the cpu fan into a system fan socket on the mobo?

System Specs:
FSP 450Watt PSU
Gigabyte P35-DS3L
Intel Core2Duo E4500 w/ AC Freezer pro 7
2 Gigs GSkill DDR2 800
Radeon HD 3850

 

[JustaGeek]

Why not? It will allow you to monitor the fan RPM.

If the 4-pin CPU fan connector is defective, disable the CPU fan monitoring in BIOS, so you don't get "false alarms",

And if your temps are OK, there is nothing to worry about,

Good luck!

 

[humanure]

it will work, personally I would RMA the board though

 

[cozumel]

If you are connecting a 3-pin connector from the Arctic into a 4-pin pwm cpu fan header on the mobo then there will likely be about a 2 second delay in the fan starting to spin. (I've never actually timed it but I think is between 1 & 2 second delay.) That delay won't cause any damage.

 

[n8thegr8]

Thanks for the help everyone, I think I've put my worries to rest. It's still idling at 24C and that ain't too shabby! The low CPU RPM still bothers me though, even under load I don't think it has gone above 700rpm. Is there a way to control or boost the rpm manually?

 

[humanure]

should be able to with speedfan.

 

[n8thegr8]

i'm rethinking whether to keep or RMA the board, is there anything that could go wrong with the fan attached to a system fan header? will it still know to spin faster when the cpu gets hot?

 

[VirtualLarry]

If you want the CPU fan to spin faster, disable "smart fan control" in the BIOS. Then all fans will run at near their max rpms. (That's what I did on my DS3R boards.)