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Dell OptiPlex 755 User Manual: Diagnostic Lights

Dell optiplex 755: user guide.
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Diagnostic Lights

Before you begin any of the procedures in this section, follow the safety instructions in the
Information Guide
To help troubleshoot a problem, your computer has four lights labeled 1, 2, 3, and 4 on the front panel.
When the computer starts normally, the lights flash before turning off. If the computer malfunctions,
the sequence of the lights help to identify the problem.
After the computer completes POST, all four lights turn off before booting to the operating system.
Light Pattern
Problem Description
The computer is in a normal off condition or a
possible pre-BIOS failure has occurred.
The diagnostic lights are not lit after the
computer successfully boots to the operating
A possible processor failure has occurred.
Memory modules are detected, but a memory
failure has occurred.
A possible graphics card failure has occurred.
Suggested Resolution
• Plug the computer into a working electrical
outlet (see "Power Problems" on page 339).
• If the problem persists, contact Dell (see
"Contacting Dell" on page 370).
• Reseat the processor (see Processor
information for your computer).
• If the problem persists, contact Dell (see
"Contacting Dell" on page 370).
• If two or more memory modules are
installed, remove the modules (see
"Removing Memory" on page 316), then
reinstall one module (see "Installing
Memory" on page 314) and restart the
computer. If the computer starts normally,
continue to install additional memory
modules (one at a time) until you have
identified a faulty module or reinstalled all
modules without error.
• If available, install working memory of the
same type into your computer (see
"Installing Memory" on page 314).
• If the problem persists, contact Dell (see
"Contacting Dell" on page 370).
• Reseat any installed graphics cards (see the
"Cards" section for your computer).
• If available, install a working graphics card
into your computer.
• If the problem persists, contact Dell (see
"Contacting Dell" on page 370).
Solving Problems



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Comments to this Manuals

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Latest comments:
  • Brian Jun 04, 2018 04:27:
    Lights 1 2 and 3 are on,compute​r won’t turn on,don’t hear fan running, little white dot flashing at top left corner off monitor
  • phi Mar 27, 2017 02:23:
  • ann Mar 22, 2017 06:24:
    i already follow the instructio​n in your trouble shooting guide but the problem is stil the same, the computer is open but the monitor and keyboard is not working. pls help.. the light is 3,4 and also the trash can drawing is lighting.
  • lawrence wright Jan 03, 2016 10:13:
    my optiplex 755 went to save power, and i cant get it to come back alive.
  • Ron Wilton Jul 27, 2014 10:52:
    What I needed to know was how to "chan​ge the battery&qu​ot;, as in the procedure itself.