Dell Dimension 8400 Fan Makes Noise

Hi,

Yesterday, when I stated my computer, the Dell started with the usual power p. Both CD bays flashed as if they were being detected by the bios, then the lights went off. Usually, the harddrive light appears to flash, yesterday it didn't. Instead of going through the rest of the boot sequence the fan in the back of the computer kick on.
The fan was getting louder and louder blowing so hard I could feel the air blowing off the back wall in my seat across from the desk.

I've never seen this before. This appears to me to be a system board problem. Can't access the bios, so I really feel lost.

I tried turing the Dell off, then waiting 10 minutes. Then turned the it back on again. Uplugged the power (with of power off) and tried several hours later and got the same results.

Hi,

Check out the heatsink over the CPU and the only fan I saw was the one which was right on the back of the machine. When running the Dell diagnostics it runs the fan up to 100% for a bit and wow, did that think make some noise. Now the fan is supposed to rev up as the heat grows from your CPU so maybe the CPU heatsink was installed wrong or whatever Dell uses to mate the heatsink and the top of the CPU finally stopped doing its thing so the CPU is running hotter and hotter.

Good luck getting it fixed

Call tech support immediately. I'd suspect the system board as well. As
preliminary troubleshooting tool, I'd also try powering the system up with the CPU fan unplugged from the motherboard.

I have seen this model fan cause a no POST situation such as yours on the 8400.