Dimension 8400 CPU Fan

I had the CPU replaced too and I saw some one that had bad memory caused the fan to go nuts.

Yes I have scanned for both spyware and viruses, and now that memory was mentioned the problem seemed to start after I added additional memory, purchased from dell, but removing the additional memory has not resolved the problem

Bob

As a follow up I received a telephone call from Dell Tech Support, they are going to replace the computer, that's good news to me

Bob

I can tell you Dell definitely has CPU FAN problems with the 8400 design though they wont give any details. What I do know is I had same problem and contacted support almost 2 months ago. First they replaced the FAN, then heatsink and then mobo but it all did not work. After lots of complaining via phone/email I finally got a replacement that is much more quit. One thing that surprises me is that the 8400 always makes the CPU fan run at same speed, while it should only run faster when CPU is heavily used. My old model run almost at max speed, and the only way to lower it was running the fan diagnostics which does a sweep from 1000 to 2000 RPM.

thermal diode of processor should normally trigger fan speed like explained on
http://cache-www.intel.com/cd/00/00/17/98/179821_179821.pdf
However it almost looks like this design neglects the cpu signal and dell just choose one speed. The second line person more or less admitted Dell had lots of these problems, and since few week they added an additional "cpufan check" when PC leaves factory. I still think its strange because we use Optiplexes at work which are very quite, only when doing CPU intensive stuff the fan will speed up for a while.
On this forum you will find lots of people complaining about the issue so there is definitely something wrong. The thermal design and component choice (heatsink/delta electronics fan) is also very weak especially compared with "real" cooler such as Zallman but hey, you get what you pay for ;-)

so what's the solution? Mine is driving me mad. I have a new fan but it's just as loud as before - a high frequency whine that goes up and down when there is even a 1% load on the CPU. I have been engaged in email with tech support and they did send me a new fan but are basically arguing with me that there is nothing wrong with anything - I know I have had over a dozen dells at my desk in the last 5 years and this one is by far the loudest and most annoying.

Same problem, but only in the games... Fan gets louder and louder until it gets to top speed. It doesn't decrease speed afterwards if I exit the game. Can't stand it.

I just had the mobo, fan and CPU replaced and it did not fix it.

They will replace the heat sink next.

I wish the support would have a better knowledge database in France to get to the point.

I just got a good solution after 4 months...
It was indeed the heat sink, but before they found out they had changed the motherboard and the CPU.
After that they have been quite unable to set the CPU speed back to 3.4 Ghz, even thought they changed the CPU again. It remained at 3 Ghz.
Then they gave up trying to fix the CPU speed, and decided to replace the machine. First they sent it to the wrong address, then they decided to send another one to the correct address.
OF course the machine I received wasn't with the exact same configuration, I had to exchange things like memory and video card...
In the end I have now a machine that runs well. I just hope it will last as I don't want to go throught the whole support cycle for 4 months again !

Had they figured out that they just needed to send another heat sink, they would have saved a lot of money.

The heat sink and fan did not solve my problem, they finally replaced the computer and the replacement was an upgrade from what I originally purchased, faster cpu, better video card, etc.

Bob