Question Computer automatically turns on when I plug it in the power outlet

[eazy11]

Hello everyone,
My issue is as follows: for various reasons I have to unplug the PC from the outlet. Whenever I plug it back, my PC automatically turns itself on for some seconds (actually the case fans ramp up, not sure if the system actually tries to boot or whatever), and then it turns off. This doesn't always happen, I've noticed it happens more often when I leave the power off for like 24 hrs. The PC is also plugged into an UPS, not sure if that matters or not. So the question is, what could cause this? After I press the power button everything boots up fine and I don't seem to have any problem at all.
I did try to replug everything, reattach the motherboard, cleared CMOS, used default BIOS settings .. nothing seems to fix this. "Restore on AC Power loss" bios setting is also disabled and I also enabled "ERP". Could it be the PSU? Or maybe there's some kind of protection, should I worry about it?
Specs are as follows:
Mobo: Gigabyte Z390 AORUS PRO
CPU: Intel I9 9900K
PSU: Seasonic Prime SSR-850PD 850W Platinum
OS: Windows 10 PRO x64
Thanks

 

[Deleted member 14196]

can you try to plug the pc into any other outlet in the house to rule out the outlet as the issue?

 

[cpotts50]

I have had similar power supply activity in the past. I suspect this is a function of the power supply energizing, and the BIOS waking up. The BIOS then tells the power supply to turn off because "Restore on AC Power Loss" is disabled. Your power supply doesn't have it's own power switch so it relies on the BIOS to check the chassis switch and turn on when requested. The BIOS would be running in standby mode (or maybe even off) waiting for the power button press, but everything else would be off.

Sounds to me like no problem, but you could check for power in the disk drive power connectors to verify power is off. Still unplug for servicing because you don't want to accidentally trigger the power button and turn everything on. 😉

 

[Paperdoc]

You could try this simple change of habit. Most PSU's have a manual switch on the back to turn it off completely. So, when you need to disconnect, FIRST shut down normally, THEN turn OFF that rear switch, THEN unplug. When you go to plug back in again, verify that switch is OFF, THEN plug in, THEN turn on that switch, and see if the computer stays off until you push the Power button on the case front.

 

[eazy11]

Thanks for the replies.
@Paperdoc i will try to do that when I get home and post here the results.