Re: 6 Beeps on Startup - No Monitor Display - Dimension 8400
About status lights and whirling fans:
On the 8400 motherboard there is a green reserve power LED lamp mounted to the motherboard inside the computer. When the motherboard capacitors are completely discharged, the LED will cease to glow.
The 8400 has four status lamps on the back plane of the motherboard, numbered one through four, visible when the case is closed and powered on. These status lights glow in green or amber depending on status. There are two more status lights on the front bezel. One is beneath the power button which glows green when powered up, amber when asleep. The second front bezel status light is to indicate hard drive activity. The floppy, and optical drives also have activity lights.
There are two key fans on a standard Dimension 8400. The first is the power supply fan and the second is the CPU fan mounted to the back plane of the computer chassis. Both of these should spin freely and quietly whenever the computer is powered up.
Lastly is the video adapter card cooling fan. Not all Dimension 8400 models were shipped like this. Most came with a passive (large heat sink) cooling system to reduce noise levels. Video adapters with cooling fans were normally high end video cards or are after-market non Dell adapter.
In the case of a whirling fan on a video card adapter, this does not mean it is working fine. It only indicates that the fan on the adapter has power. The adapter card still may be misaligned in the PCI-e slot. It is not at all uncommon for the steel bracket which is inserted into the chassis backplane to become misaligned with the chassis causing the adapter card to look fully seated when in reality it is not. Viewing the installed adapter card from the wide surface along the pin edge of the card should indicate a uniform line along the entire row of pins when compared to the adapter slot. If the card appears slightly higher nearest the backplane or at the rear it is misaligned. It still might work for a short time but cease when the limited contact surface is disturbed.