Weird CPU fan issue.

Dell Dimension 4500 desktop
December 9, 2009 at 21:16:29
Specs: Windows XP, P4/512MB
My wife called me at work today and told me that the fan on our computer got loud, then it got quiet, then it got loud again, etc. (almost like someone was flipping a switch back and forth). Eventually the CPU fan stayed loud. At first I thought it was just a rampant program causing the CPU to run hot. When I got home and listened to it, it turned out to be something completely different. The CPU fan is loud. But, not in a bad way (i.e. bad bearing or a blade brushing against something). It's a normal fan noise...just much louder.

By the computer is idle while the noise is being generated (no rampant programs).

I recently cleaned out the tower so there was virtually no dust inside it. I did clean what little dust there was out.

While my tower was open, I unplugged the CPU fan and turned my PC on. I heard the PSU fan running. Though I don't believe that it's blowing as much air out as the last time I had my hand back there. (but, that could just be my mind playing tricks on me).

I plugged my CPU fan back in and closed the case. I then proceeded to search the Internet for fan problems. All of the problems I read dealt with too much dust in the case or a physical defect of the fan. I haven't found anything describing the issue I'm having.

I must say that there is a pretty good breeze coming from the back of our computer now and I don't think the case has ever been as cool as it is now. :-)

My theory is that for the past 6'ish years that we've had the computer the PSU fan has managed to keep the case cool enough. Now, there's something wrong with it and the CPU fan has been activated to take up the slack.

I am worried that something might be going wrong with the power supply. Is there any kind of diagnostic software for power supplies? I did install SpeedFan. It seemed to recognize that I had two fans, but it could not read them. Nor could it tell me the temperature of my system.

I would appreciate any input that anyone has. Is my theory sound (I'm a coder not a hardware guy so to me it sounds good)? Has anyone encountered anything like this? Do fans have baffles that help them run quiet? If so, could it have fallen off of mine?

Again, any input would be appreciated. Thanks in advance.


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December 10, 2009 at 02:24:40

You can try the following:

- Re-apply the CPU Thermal Compound
- Try another fan to see if it`s noisy again ( don`t buy it, find one to try it )

Go to BIOS and check the CPU Fan Speed & CPU Temperature.....then POST them back...

Google is your friend

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December 10, 2009 at 07:57:36
u had it 4 6 years thats good. mine last 2. its not bad my pc does it and its clean. just buy a new fan if u cant live with the noise btw what ur power supplie 750 or 1000 watts

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December 10, 2009 at 19:14:05 I said in the original post...I'm a coder. I described my issue to a friend of mine who builds his own machines. I called it the CPU fan because of the cone that covers the fan and the heat sinks. My friend educated me by telling me that CPU fans actually sit on the CPU. Color me embarrassed. :-)

He told me the fan I'm having trouble with is the exhaust fan. And even though it sounds normal, he says it's probably the bearing in the motor.

I'm going to stick with coding. ;-)

It's all a moot point anyway. The fan died while I was at work.

Thanks to those who responded.


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