PC turning itself off and on again

jamman · 21 Aug 2020 at 11:24

Got an odd one on an older PC and before I start looking at replacing parts or the whole thought Id get some opinions.

PC has been sitting there doing its thing no problems, then started rebooting randomly. It doesnt lose power immediately, it goes to windows shutting down so power isnt being cut.

Brought it downstairs and problem went away for months (suggesting possible loose connection?)

The other day shut down and since then an sit there rebooting at random times, and if I power it off can even power itself back on.

Updated mobo bios and it stayed online for a day then started again.

Ive tried:
Checking temps arent too high.
Checking cabling
Replacing PSU
Tried a new SSD with new windows and literally started doing it during the build.
Removed Gfx card
Reseated RAM

Its very weird, its almost like the problem is with the actual power button sending random power on/power off signals (or the mobo thinking its getting them)

Anyone have any thoughts?

mickyflinn · 21 Aug 2020 at 11:35

Set the windows power management to max also disable computer going into sleep mode.

jamman · 21 Aug 2020 at 12:32

mickyflinn said:
Set the windows power management to max also disable computer going into sleep mode.

Checked all that. Never set a PC to sleep myself.

Wouldnt explain the PC turning itself on either.

And more tellingly, it does it even from inside bios.

postmanfw · 21 Aug 2020 at 12:40

Check the power switch that's built into the case....seen it before where a build-up of dust was causing the switch to activate itself...or it could just be faulty...try disconnecting it from the motherboard and just start pc with a screwdriver by shorting out those two terminals as a test to see if it stops.

Robert T. · 21 Aug 2020 at 12:52

What OS you have there?? Win10 is notorious for enforcing updates that he deems 'important' and 'mandatory' and restarting system.

jamman · 21 Aug 2020 at 12:53

postmanfw said:
Check the power switch that's built into the case....seen it before where a build-up of dust was causing the switch to activate itself...or it could just be faulty...try disconnecting it from the motherboard and just start pc with a screwdriver by shorting out those two terminals as a test to see if it stops.

It does seem like the power is being told to switch off, hence windows says shutting down.

Ive disconnected the power button completey for now, the reset button is still active so that will at least rule one thing out.

jamman · 21 Aug 2020 at 12:53

Robert T. said:
What OS you have there?? Win10 is notorious for enforcing updates that he deems 'important' and 'mandatory' and restarting system.

ITs not OS related, it does it in BIOS, and if the PC Is off it even turns on

jamman · 21 Aug 2020 at 18:32

Up for 5 hours so far.
IT did stay up for 27 hours though the other day so no celebrating yet

t31os · 25 Aug 2020 at 06:30

You should be able to use the reset and power switch on the case interchangeably, they both perform the same function(jumping a connection between 2 pins), you could use the reset button on the case as the the power on button for now, leaving the usual(potential problem) one disconnected.

jamman · 25 Aug 2020 at 13:41

It was definitely the power button, stayed on for days when disconnected, put it back on and turned off within minutes.

Good suggestion about using the reset button, that will do for now. Its an old PC that just runs Plex Server so no big deal.

t31os · 25 Aug 2020 at 21:20

Could be a build up of dust bridging the connection(can happen), might be worth seeing if you can get at the contacts of the switch to give it a clean.