PC turns on and BIOS resets when I plug my PC in.

Something really strange.

If I turn on my PC with the case button (and, for that matter, the 'start' button on the mobo) the PC begins normally.

If I plug my PC into the wall directly, the PC turns on by itself and the BIOS resets. I don't think it's a dying CMOS battery as the BIOS settings are kept if the PCs turned off and on using the power switch.

I've posted this in power supplies as it's obviously to do with power. Really though, I've no idea where to post it.

Thanks in advance,

9 answers Last reply
More about turns bios resets plug
  1. It is a dead CMOS battery. The PSU is working, even if you use the case power switch. And a CMOS battery is cheap, so try that first.
  2. If bios not saved then it was dying batt or u had fail / broken BIOS chip.. (Even it saved sometimes if it weak then it had trouble detecting HDD / optical /etc..)

    I'm still confusing what do u mean by "If I plug my PC into the wall directly" .....

    "If ...... the PC begins normally. " where u plug the power cord to (power strip / voltage regulator / UPS / wall) ?
  3. I'll pop out later and get a new CMOS battery. Give that a try.

    @rdc86 - excuse the poor explanation. I live in The Philippines where the wall sockets and plugs look like this

    i.e. as soon as the plug is put into the socket, there's power coming from it.

    If I plug the PC into the wall / powerstrip etc, the PC turns on and the CMOS resets without me touching the power buttons on the actual PC tower.

    If I turn on the PC using the power buttons on the mobo or PC tower, it begins normally and the BIOS settings are as I left them.

    Hope that made sense.

    I'll post back if a new CMOS battery solves the problems. I'd understand that the CMOS battery being dead explains the loss of BIOS settings, but could it be responsible for the PC turning on without me touching the power switch?

  4. Hehe looks like we are on same continent :D....

    If it turn on without pressing the power button, just by inserting the power cord to the wall...

    can u try check in the bios... especially the setting that about power lost...
    it usually had 3 option, a. Stay OFF, b. Restart, c. Remember last state (ON/OFF)..

    It manage how the computer react when power back (plung power cord in your case) on if there power loss (unplug the power cord in your case)...

    I guess it set to b. restart
    so make sure it set to a.stay off... (b. or c. usefull if u running server / gateway / 24h comp)

    if the setting are correct and it still happen then we will move to next step..
  5. thanks for the replies.

    Replacing the CMOS battery didn't solve the problem. It's still losing settings and jump starting* when plugged in to the wall directly.

    It wasn't / isn't set to reboot after a powerloss.

    *don't know if that's the correct term...
  6. Hmm.. this kinda bad, I'm kinda hoping changing the batt will solve it

    How the voltage reading of the PSU?, it can be find in bios or using 3rd parties apps (hwmonitor/oocp/etc..)

    Could u try using other psu?
  7. Hi there,

    Which voltages? Which lines? I'm away from the PC at the moment but can post in the next hour or so.

    It's a corsair HX850 PSU. Only about 9 months old. I know that doesn't mean that nothing will go wrong, but less likely than a cheapy one.

    I've got another PSU but not one that would run my system (SLI GTX470's).

    I've put the CPU back to stock settings. It was OC'd.

    The RAM (4 x 4Gb) needs a bump in voltages to be stable - stock volts there mean the system freezes when more than half the RAM's in use.

    Is it likely to be a short somewhere? I can everything out of the tower and rebuild it, adding one 'thing' at a time (fans, hard drives etc.). I've a homemade test rack.

    My gut feeling is a dying mobo... the only component I don't have a spare. Maybe time to get that i7 upgrade :)

    Is this likely to be something that can kill other components if I just ignore it?

    Thanks a lot
  8. The PSU just for testing for power on to eliminate the PSU/Mobo, (try with one 470 un plunged..) see if it same thing happens...

    if the same thing happen then it could be the mother board, if the problems stop mostly the PSU the culprit...
  9. Thanks for the replies.

    I think it must be the motherboard. It's not shorting as it did exactly the same built up out of the case and with only my SSD, keyboard, GPU and monitor connected. I did it with an old GPU (that runs fine in another PC) and a different PSU.
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