Dimension 9100 won't start, flashing yellow light.


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Dimension 9100 won't start, flashing yellow light.

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I have a Dimension 9100 running XP home edition that won't turn on "normally", there is only a flashing yellow light when the computer is plugged on. After clearing the CMOS, checking cables etc., I tested the voltages on the psu with a multimeter, using a paperclip to short the green and ground, and everything was where it was supposed to be. I eventually was able to start the computer by shorting the green wire with a black one while the connector was plugged into the motherboard, this caused the computer to start up and continue running after I removed the paperclip. I restarted the computer, and it rebooted correctly. But when I shut it down, and tried to start it again with the power button, it didn’t turn on, the flashing yellow light returned. When I pressed the power button to turn it on that time, the fans and drives started for less than a second, then stopped. I tried starting it again with the paperclip but this time it went to a screen displaying information about my video card and just stayed there. I tried again with the paper clip and it started normally. I also tried starting it with a good psu with no results. 

I found other people with the same problem who had said that broken USB ports in the front had caused the problem, so I replaced the front i/o panel with a new one with no results. The ports in front were broken, but the ones in back look okay visually. 

I followed the troubleshooting guide and didn't get any results so I don't know where to go now other than a bad mobo. I don't know how the computer could start up though if the motherboard had been damaged? Even if you don't have any answers for my question, I'd really like to know if a computer can start up with a problem in the motheboard.

Intel Pentium 4 630 Prescott 3GHz 
ATI Radeon X300 
650 watt Antec PSU(this original psu was replaced about 18 months ago when the fan inside started making a loud noise) 
3 gigs ram 
320 gig hard drive 

Thank you! 

All Replies
  • What color are the 4 diagnostic LEDs on front of the tower when it won't boot?

    You may have to strip it down to bare essentials. Disconnect all drives, except boot hard drive, remove all PCI cards except video card, remove all RAM modules except for the one in slot 1.

    Then remove the motherboard battery and press/hold power button for ~30 sec. Reinstall the battery (right-side-up!) and see if it boots now with only mouse, monitor and keyboard connected. If that works, add back hardware, a little at a time to see if you can ID the bum part(s).

    Always power off, unplug and press/hold power button for ~15 sec before doing anything inside the case.

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    Forum Member since 2004

    I am NOT a Dell employee

  • There were no diagnostic lights. I tried that and I didn't get anything. I even removed everything from the mobo except the two psu connectors and io panel connector with no result (I don't know if it would do soemthing though.)

  • If it still boots up when you jump the power supply with a paperclip, then you may have to suspect the front power button and/or front I/O panel, itself.

    Are you sure the replacement front panel works OK and was connected correctly to the motherboard, and that little cable between motherboard and panel is good?


    If this answers your question, please click  Yes  


    Forum Member since 2004

    I am NOT a Dell employee

  • I can't say for sure that there isn't a problem with it, but once I start the computer, I can use the power button to turn it off. so I'm assuming that if it works to turn it off it would work to turn it on. Also, when I've turned it off after working, the button works to turn things on for a tenth of a second before going to flashing orange.

  • How do you jump the power supply with a paper clip?


  • By connecting the green wire with any ground(black) wire.

  •  rosiek32

    Unplug the cord from the power supply, hold the power button in for about 15/20 seconds and open the case.

    Remove the 24-pin power connector from the motherboard and use a 'Jumper' between the Green and Black connectors of the 24-pin plug, allows the PSU to bypass the front panel on/off switch.

    Jumping means you use a small lenght of thin wire, [or use a paper clip, bent into the shape of a "U" ] then pushing one end of it into the green wire pin and the other end into a black wire pin, touch the metal inside the plastic housing, to complete the circuit between the two.

    Do not pull any wires out of the plug.



    If my answer was helpful, please use the 'Did this answer the question' and click: Yes
    Forum Member since 2001
    I am not employed by Dell