System won't boot with front panel switch - Dimension 8400 - General Hardware - Desktop - Dell Community

System won't boot with front panel switch - Dimension 8400


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System won't boot with front panel switch - Dimension 8400

  • The Dimension 8400, purchased 4 yeasrs ago, suddendly froze up and would no longer boot.  The rear panel lights and the front panel switch light would not light at all.  When power is disconnected and reconnected the power supply (REV A04) and fans briefly enable and after 1 sec. disable.  But no system boot.


    I have completed the following diagnostics: 

    1. Cleared CMOS (disconnect power; wait for MB light to go out; removed battery; cleared pushed front panel button for 30 seconds;reset battery; reconnect power).  *** The system actual boots up after 2-3 seconds.  But on the next shutdown the problem comes back ***


    2. Same as above but start the system without the battery reinstalled.  *** Same result - The system actual boots up after 2-3 seconds.  But on the next shutdown the problem comes back ***


    3. a) Removed all components (disconnect power; wait for MB light to go out; removed battery, NVRAM, cards; reconnect power).  MB lights and beeps.  DELL Tech informs me this is the MB complaining that there is no NVRAM and an indicator the MB is OK. 


     b) Then disconnected power and installed one NVRAM in Slot 1 and connected power back to system.  System does not boot.


    c) Tested NVRAM in another system.  Both (had 2 x 512MB) were bad!!  Purchased new NVRAM and installed only one back into slot 1.  Added back all cards checking for goot connector fits and card connections.


    d) System reboots only if #1 and #2 above are done.  Front panel button switch does not work but light is green on the front button.


    4. Configured BIOS Power Management so Reboot when power restored after outage is set to ON.  Disconnect power for 30 seconds so the MB light goes out.  Reconnect power and 2-3 seconds later the system boots up no problems, all lights green, no errors.


    So I can keep the system going so when finished with it, shutdown as normal, disconnect power at back and reconnect power at back when the system is again needed (time disconnected from power must be greater than 30 seconds).  The system automatically boots up when power is restored at back of system.


    I hope, should someone have experienced this problem, provide me kindly with insight to the following:

    • CR2032 3V Battery voltage (used multimeter) is 2.86V.  Is this too low?
    • Is the battery somehow connected and needed for the front panel button switch to operate?  LED works but the button swicth functionality does not. ????

    Any insights into this dilema whould be greatly appreciated.






  • The only thing that comes to mind is a weal power supply preventing you from doing a reboot. I would not purchase one based on my opinion, but if one was available for testing that would be my next trouble shooting step. You would be well to have 400 or better watts available. Note, most replacement power supplies will not fit the Dell case but if you are handy with a Dremel tool some of the case’s can be made to accept the standard power supplies.

    Cheers, Dave
  • oops weal=weak!   duh!
  • 12lrn4evr

    I think, you are refering to 'memory', this it not the NVRAM [Non-Volatile Random Access Memory]. The 8400 motherboard has four DDR2 memory slots.

    First, just replace the CR2032 3V coin cell battery, a replacement only costs about $2 and can be purchased from most computer stores, pharmacies, or a Walmart.

    Open the case and check power cables, by removing and reseating them, also check for any charred or burnt connectors, especially the 24-pin and the 4-pin power connectors on the motherboard, also, check the motherboard for any capacitors with bulging tops or are leaking.

    Then if you are comfortable around computers, you could try the following to test the power supply.

    Unplug the cord from the power supply, hold the power button in for about 15/20 seconds, open the case, unplug the 24-pin power connector from the motherboard and jump the Green wire to one of the Black wires, reconnect the power cord and power the system on, if power supply fan and hard drive run, then the PSU should be good.

    Note: Do not remove any wires from the plug, use a small piece of wire or a paper clip as a jumper.

    Power supply checks out and the system still does not work, again remove the power cord, hold power button in for several seconds to discharge the residue power, reconnect the 24-pin connector to the motherboard.

    Remove all the PCI cards, the video card [if applicable], memory, all peripherals, disconnect the data and power cables to all the drives, then check that the front panel cable is connected to motherboard, with nothing else connected to the system, reconnect the power cable and power the system on.

    If you do not get any beep codes or diagnostic lights on the front/back panel, then it would appear that motherboard has died.


    Please don't send me questions about your system by DCF Messenger.
    Post the issue in the appropriate Board, where they will be answered.


    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

  • Digital28,


    Thank you very much for your reply.  I will check my power supply output.  However the power is enough to drive the system once the battery is replaced and the system BIOS Power Management is set to Reboot when power restored after outage is set to ON. The only thing that now appears wrong with the system is that after a shutdown I cannot restart the system with the front power button.  I must disconnect the power, wait 30 seconds for the MB green light to go out, then reconnect the power.  The new BIOS Power Management setting causes the system to boot up automatically.  All is well.


    So the power drives the system.  There is no error messages on boot.  All lights are now green.





  • Thanks Shesagordie.


    I will replace the battery Tuesday - long weekend in Canada - to be sure.  I have been searching the web but so far unable to find the CR2032 tolerable voltage levels.  Mine measures 2.86V.  This seems close enough to 3V and does maintain the NVRAM BIOS settings, etc.


    The power cables and capacitors are all OK.


    When all cards and memory are disconnected the MB beeps .. Therefore it appears the MB is OK.


    I will validate the Power supply .. thank you for the instructions.  But as I commented to Digital28, the power supply seems to be working great powering everything on the system.


    I am beginning to suspect the front panel power switch is broken.  Yet the LED still works.


    Thanks ..