Hey guys, I have a Dell Dimension 8400 desktop computer. For the last 2 years its been working pretty good, but recently Ive been having problems with the fan. I'm not sure if its the fan on the gpu, the cpu, or the tower fan, but about half the time when I turn on the computer, the fan begins to roar like a car engine, its blows tons of air out the back of the tower, and the monitor stays black. Anyone have an idea as to what's happening? My computer works about 1/2 the time, which leads me to think that it cant be too serious... also, it plays games really well when its working. Here are the specs on my computer in case youre curious. Intel Pentium 4 3.2 ghz 1 GB RAM 160 GB hardrive Nvidia Geforce 6800 gt 256mb ram
Open the system to see which fan the noise is coming from on the inside. There may be dust caked up on the processor fan as well as the power supply fan. You can get a can of air and blow the dust off. Sometimes this will resolve the issue. If the processor fan is clean and is making the noise it will need to be replaced. This is true for the power supply fan as well.
Fan roaring plus black screen means the chipset and BIOS POST never got as far as loading the fan control constant, one of the first things it does. Remove dust, reseat connectors and memory, check the diagnostic lights for an error code. Check P2 (2 ylo, 2 blk wires) for discoloration (brown).
If none of those produces any results, and you can hear the harddrive spindle up (confirms 5V and 12V power) you're looking at motherboard failure.
While you're in there, check all the capacitors on the motherboard. They look like little metal cans on the board, typically black or blue. They should be perfectly round with flat tops. If any are bulged or leaking, replace the motherboard.
The jpg by contrvlr in this thread is pretty graphic evidence of a bad capacitor: http://snipurl.com/1v2ab