PC switches back on by itself after powering off

[gui_m]

Hi,

I've built a few systems already before, but I've run into some trouble building my latest one.

Everytime after I switch off the computer, either through windows shutdown or through the power button, the computer switches off and after 4-5 seconds, it powers itself back on! It's quite annoying as the only way to shut it down is the switch at the back of the PSU.

I don't know what I've done wrong. I would guess that it's to do with the Power header where i connect the case to the MB, but I've checked that and it seems to be alright.

What else could be causing this??

Thanks for your help!

Edited June 6, 2008 by gui_m

[gui_m]

I was playing about with the cabling, and I found that the computer does not switch itself back on when I unplug the ATX 12V PSU cable that goes in the MB... However, I fail to see anything on the screen when I do so, so leaving it unplugged is not an option...

(it's this guy here that I'm talking about):

I'm not sure if this is really relevant, cause the PC shouldn't work without this cable, but i guess it might help.

Edited July 14, 2008 by gui_m

[puntoMX]

I would think of a short at the back of your motherboard or the board itself, or a faulty PSU. Try swapping them out and start with the PSU.

[RJM]

Did you disable WakeOn lan in BIOS? If not, try that.

Edited June 6, 2008 by RJM

[gui_m]

thanks for the quick reply. I don't really have another PSU or MB to test if it's faulty. I will test them if when I get my hands on one later.

Anyways, I've began to think it's BIOS related. I have a Gigabyte EP35-DS3. I went into the BIOS option and found some options under that I think could be related:

AC Back Function

Soft-Off by PWR BTTN

I messed around with these, but no luck. Any other BIOS setting that could cause this? Tried disabling wake on LAN, but still nothing

Edited June 6, 2008 by gui_m

[shahed26]

Try restoring your BIOS default settings, (Before Restoring, make sure you note or backup your current BIOS settings)

[gui_m]

Try restoring your BIOS default settings, (Before Restoring, make sure you note or backup your current BIOS settings)

No luck... gonna try a BIOS update in a bit but starting to think it's not the BIOS...

[Smiley357]

Did you mistakenly set power switch to the reset switch on the motherboard?

[gui_m]

Did you mistakenly set power switch to the reset switch on the motherboard?

Haha I wish that was it cause it's starting to frustrate me! spent all day trying to fix this...

[Tripredacus]

In the power section of the BIOS, you may see a "Resume" option. If it is enabled, it allows you to choose from a series of numbers. One of our customers uses this because the PC doesn't always turn on after a power failure, so they used it to make sure it turned on. I don't know how it works or what the numbers mean, but I know you can just try disabling that.

The name is different in various BIOSes but its usually under the ACPI type (S1 or S3).

[Oziyn]

Im pretty shur its a problem with your psu because if it works when u unplug those cables then its definatly not your settings. Maybe you need to buy new cales for your psu. they only cost like 12 bucks for a big pack.

[gamehead200]

If none of the above work, check the power button itself; it may have a short somewhere and cause the computer to power back on. Although, if this were the case, then your computer would probably be shutting down spontaneously as well, so I'm not 100% sure. Like a few other people have already mentioned, swap out the PSU and see what happens.