Low RPMs on case fans?

[JeffSeveringhaus]

I'm running a 2.4 ghz p4 on an asus P4PE motherboard, and my idle temperature is aroun 40C with an ALPHA 8942. Today I bought 4 case fans that have a 50.2 cfm rating, but when i plug them all in they are only reported on MBM 5 as running at 2000rpm. Is there any certain way of wiring that could cut the rpms?

 

[mechBgon]

What motherboard do you have that you can plug four additional case fans into, or did you test them one at a time, or is there another explaination?

 

[GiZzO]

1. They are wired wrong like ground is going into yellow, though i think this would result in no rpm or faulty reading...but it does make the fan run half speed.
2. The fans are too much of a draw for the fan headers.

Solutions:
1. Compare the wiring/pin layout with another fan that has a 3-pin connector that worked properly.
2. Get a RPM 3 to 4-pin adapter, this will allow to draw power directly from the power supply this way your fans will get that power it needs, without the worry of your fan headers burning out..and you'll still get your RPM reading. PM me on where to get RPM adapters.


GiZzO's Fan Database Page

 

[JeffSeveringhaus]

It's a ASUS P4PE/L based on the Intel 845PE chipset. I have 4 of the fans hooked up to psu through the the power supply, while the cpu fan is plugged in to the mobo 3pin connector.

 

[mechBgon]

I see. Unless the fans have special connectors that draw power from the PSU while sending their RPM signal to the motherboard, they're not going to be detectable by MBM5. If you wanted to monitor the RPMs on those fans and control them, a Digital Doc 5 might be a nice little goodie: link These can also be found in silver or black at various cooling merchants.

 

[JeffSeveringhaus]

Ok...so now i understand why the 4 case fans aren't coming up, but i still don't get why my cpu fan connected through the 3-pin motherboard connector is only running at 2000rpm...i tried adjusting it in the bios, but it wouldn't let me change the value.

 

[mechBgon]

Generally you can't adjust the speed of the CPU fan directly in the BIOS. It's sort of like a car that has an oil-pressure gauge... it's there for informational purposes, you can't use it to adjust the oil pressure.

Now, if you look on page 4-33 of your P4PE's manual, you can enable Q-Fan, which you can enable if you want to trade off some CPU cooling for a lower noise level. It will run your CPU fan even slower than normal (but never faster than normal) if the CPU is running below a certain "safe" temperature. If the CPU's temperature exceeds the temperature it's trying to maintain, it will begin incrementing the voltage up on the CPU fan again until it stabilizes the temperature rise.

 

[Jeff7]

Originally posted by: JeffSeveringhaus
Ok...so now i understand why the 4 case fans aren't coming up, but i still don't get why my cpu fan connected through the 3-pin motherboard connector is only running at 2000rpm...i tried adjusting it in the bios, but it wouldn't let me change the value.

Is that what MBM5 says the speed is, or BIOS? If it's MBM5, it's possible that the fan divider isn't set correctly.
What fan is it?

 

[JeffSeveringhaus]

I know it isn't name brand, but the fan is called a "PC Toys Crystall Maxx"...it's an 80mm clear case fan. Could it be that my PSU isn't supplying enough power? It has a 450w psu by foxconn. Would the fans run at full speed when hooked up to the 4pin connectors along with different periferals? My cpu temps are now up to 44C. I was running at 41 idle with my stock cooler

PS. The alpha 8942 says the fans should be blowing away, but i've heard people say either way works. Any experience here before i switch it up?

 

[mechBgon]

Hmm, I bet you have Q-Fan enabled in your BIOS and the motherboard is slowing down your fan as Q-Fan is designed to do. You can tell very easily... let the computer run for five minutes, then reboot it. If the CPU fan audibly picks up speed at reboot, Q-Fan had slowed it down on you (this assumes you can hear this fan over the noise of the others). Or just refer to the manual, page 4-33, and go into your BIOS to check whether Q-Fan is enabled. If you want your fan to run at full speed all the time, disable Q-Fan.

 

[OulOat]

Listen to mech.

 

[amcdonald]

Originally posted by: OulOat
Listen to mech.