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Dell dimension diagnostic lights

Mike_Sumner asked
I have a Dell Dimension 2400 desktop that has been having a lock up issue.
The powerlight turns orange and the hard drive activity light goes solid green.
The computer does not power down but is completely unresponsive.

On the back of the CPU just below the mouse/keyboard inputs there are four diagnostic lights labeled as "A,B,C,D". A,B,C are lit solid orange and D is off.

I have the Dell Diagnostic lights chart form the Dell website but this light combination is not listed.

I have repalced the power supply and did reseat all of the memory / CPU / and cables.
The same problem still happens after 24 to 36 hours. All fans are working properly.

Does anyone have any idea what the lights mean on the back? Dell can't help and I can not find this specific sequence anywhere on the internet.

Thanks in advance!
Watch Question

Suspect your motherboard is gone.  However other thoughts:
What memory sticks are you using?
Do you get any beep codes?
do you see any bulged or blown capacitors on the motherboard?
diagnostic Lights page for other contributors:
An orange power LED indicates a failed power supply or motherboard. Since you have already replaced the power supply, motherboard has likely failed and the diagnostic LEDs are not operating properly.


I'm starting to lean to the motherboard being bad also but I was hoping someone might be able to identify the LED code.
I do not see any thing that looks suspisious on the board itself. I do not get any beeps that I know.

This box seems to go down in the late evening hours, would the beep codes be continous or does it stop beeping atfer a while?

I have the same Dell document at the link above but again, my specific LED code is not listed.
Distinguished Expert 2019

can it be overheating?  install speedfan to monitor the temperatures : http://www.almico.com/speedfan.php


This turned out to be a bad embedded video controller. The video chip is bad and shutting downing the entire motherboard.

Thanks for all the help!

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