CPU and case fan spin down while running

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I just bought a socket 478, Intel i865 chipset motherboard as a
replacement for an Asus board that seemed to have a failed AGP
slot. The Intel board is apparently new, a Gateway OEM board,
ordered from PC Parts Unlimited...

I installed the board, and hooked up everything 100%, confident
that it would have no problems. But low and behold, as it was
starting to boot into Windows, I watched the CPU fan spin down to
0 RPM. I shut it down immediately and started the PC again and it
of course did the same thing, CPU fan came on with everything
else, but then spun down after running for about 3-4 seconds. The
CPU fan spin down seems to have no immediate affect on the rest of
the system. It would be happy to boot up into Windows if I let it.

I disconnected the case fan and hooked the CPU fan into the case
fan header, and it still did the same thing. I completely removed
the board from the case, layed it on a non-conductive surface, and
powered it up. Still the same thing. I removed the heatsink/fan
and plugged it into a spare fan header on an old 440BX board, and
it ran fine. This heatsink/fan came with a retail boxed P4 CPU.

I've tried both an Antec Basiq 500W, and Thermaltake 430W PSU just
in case someone thinks its the power supply.

Its strange that the CPU fan will shut down no matter what header
it is connected to. On at least one occasion both the CPU fan and
case fan spun down. It may be doing it every time, I don't leave
it on long enough to watch the case fan spin down all the way.

I'm thinking I will have to send the board back to PC Part
Unlimited. I plan to email them first to see if they have any

Thanks in advance for any advice

Re: CPU and case fan spin down while running

E wrote:
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If the board is worth keeping, you could bypass the powering issue,
with a fan adapter cable.

This one solves only the powering issue, and doesn't solve the need
for the motherboard to get a fan RPM signal. The idea is, to get
+12V and GND from a Molex disk connector, and onto an LP3.


This discontinued product from Antec, has two fan connectors per
Molex power connector. The male three pin fan connector, provides
+12V and GND to the fan, so it will run at full speed. The female
connector, with the one white wire on it, carries the RPM signal.
You plug the female, to the CPU fan header. By doing that, the
RPM signal from the fan, is received by the BIOS. Some BIOS check
for an RPM signal, and shut off the motherboard in a few seconds,
if no CPU fan RPM signal is detected.


So you may want a product something like the Antec one. Another
example of an RPM enabled one, here.



Re: CPU and case fan spin down while running

i have had this problem before,i would try shorting the reset pins. you
reset button might be faulty

Re: CPU and case fan spin down while running

Paul wrote:
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Thanks Paul, I did think about getting some sort of an adapter to
run the fans directly from the PSU, but was indeed worried that
the BIOS would think that there where no fans connected. Didn't
know the device you mentioned existed.

But hopefully, I won't need to do this. See my reply to Calab.


Re: CPU and case fan spin down while running

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My AMD dual core Opteron machine does the same thing. The fan is temperature
controlled and only comes on occasionally. The fan runs full speed while the
BIOS starts the PC, but once that's happened the fans spin down and Windows
loads fine.

What you need to worry about is if the heatsink is getting very hot, or if
the BIOS temperature monitor shows the CPU temps shooting up.

Re: CPU and case fan spin down while running

Calab wrote:
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Thanks for the reply. I think you hit the nail on the head.

I just received an email back from PC Parts Unlimited's tech
support, and they said the same thing. That the CPU fan speed only
runs when the BIOS senses that the processor is starting to get a
little warm. I didn't think hardware of this vintage with a P4
would have this feature, but there was a hunch in the back of my
mind (for some reason) that it was a simple BIOS feature. But I
was afraid to leave it on long enough to check. I haven't tried
the board again since I just learned this. Hopefully thats all it is.


Re: CPU and case fan spin down while running

On Thu, 12 Jun 2008 22:41:24 -0400, E

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Check your bios for fan throttling settings.  What you see
occuring is usually due to a fan throttling setting, set to
aggressively for the particular fan that is attached.  The
resolution is to turn off the throttling altogether or set
it to a lower temp, and/or higher percentage or ratio.

Of course if worst came to worst you could get the adapters
another poster mentioned.

Re: CPU and case fan spin down while running

E wrote:
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The spin down was in the motherboard design and can be changed in
the motherboard firmware as mentioned by other posters, and PC
Parts Unlimited Tech support.


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