Helping people with computers... one answer at a time.

Computer turning itself on at night could be the result of a faulty switch. It might not be an easy fix mechanically although there is one easy solution.

About a year ago, I shut my desktop down for the evening and the next morning, the desktop was turned on. Thinking maybe I'd clicked on Standby instead of shut down. I carefully shut it off that evening. The next morning, I could hear the fan running and the light on the Power button on the tower was blinking. That night I shut it off by holding the power button on the tower until I heard it shut off. It was back on the next morning. Now I've lived alone for the last eight years and have only one house key. I tried reformatting and reinstalling XP a couple of months ago, but the problem has not changed. I've been unplugging the power cord for about a year, otherwise it will be running when I wake up without fail. No problems with my laptop. Any suggestions would be greatly appreciated.

In this excerpt from Answercast #76, I look at a computer which mysteriously turns itself on each night. No, it's not ghosts!

Computer turning itself on

So, there are two things that come to mind.

One is fairly unlikely, but I have to mention it anyway. That is: sometimes there is a protocol for allowing your computer to wake up, or to power on, in response to a particular kind of network message. Now, of course, when you turn off your computer, most computers don't turn themselves completely off. There's usually something (even if it's just to keep time) that keeps running on those machines.

When that option is configured, the network card actually remains somewhat active and it keeps monitoring for this "wake up packet," if you want to call it that.

It's rare. It's really rare that it would happen in a home situation. This is something that's more commonly used in a corporate or industrial environment. I mention it for completeness because it's one of those things that, maybe, could be factoring into this.

It's typically a BIOS setting that you can turn off. So I'd have you look into your BIOS to see if that were the case.

Power switch problems

The more likely problem is the power switch itself of all things.

Many of the power switches that we use are actually... I want to say ...not really "hard" switches. They don't actually switch off the power. They are typically a very small, low voltage switch that then triggers a higher voltage switch that actually deals with the power.

So what you're actually pushing on is something, typically, that turns out to be fairly cheap. It's not like the light switch on your wall; it's more like a keyboard key that instructs the computer to turn the power on or turn the power off.

If that switch is (for whatever reason) kind of, sort of intermittent, then when the computer is running, you'd never notice; because even if that switch were hit just briefly, the only time the computer (when running) is going to respond to that switch, in most cases, is if the switch is held down for a long period of time. That's not the case with an intermittent switch.

If on the other hand, at night when the computer is turned off, the switch (for whatever reason) decides to maybe "spark" or a little bit of static electricity maybe sets it off; that could be confused by your computer as an instruction to turn itself back on.

Unfortunately, I don't know of a really great solution for this one.

I mean, the power switches are kind of a pain to replace, if you can even get the parts. My recommendation (in fact, the recommendation that my assistant ran into when he was looking at this question) is to get yourself one of those switched power strips. When you turn your computer off at night, after everything has been turned off, hit the switch on the power strip, too.

That's the moral equivalent of unplugging the machine like you've been doing this entire time. But it is going to remove all of the power from the computer and ensure that it can't start up no matter what the case.

So those are things that come to mind. Power strip: it's not an elegant solution, but it's a practical one and it can certainly last until you get yourself a new computer some day.

(Transcript lightly edited for readability.)

Article C6103 - December 5, 2012 « »

Leo Leo A. Notenboom has been playing with computers since he was required to take a programming class in 1976. An 18 year career as a programmer at Microsoft soon followed. After "retiring" in 2001, Leo started Ask Leo! in 2003 as a place for answers to common computer and technical questions. More about Leo.

Not what you needed?

Neville Bates
December 5, 2012 6:39 PM

My sister had her computer starting up during the night and dialing a phone number through the modem. It turned out that a repair person had put a dialer and other software on the machine while repairing it, so that he could get it to dial up porn sites. He has spent time in jail as a result of this activity as he had been putting it on most of his customers' machines!
I guess it is unlikely to be the cause of this particular issue, but something to keep in mind.

December 6, 2012 6:55 AM

There is a third option that can cause this behavior.

Most BIOS has a power management option that turns on the machine at a specified time. I have used this for many years to keep my machines - both personal and work, ready for use. Saves on booting time. BTW if the machine happens to be on, this command is ignored.

To resolve this probkem, go to bios - power options and ulselect or turn this option off.

Rick Sos
December 7, 2012 9:25 AM

I had that same problem two years ago. Only I was sitting beside it when it turned on so I knew there were no pranksters. My friendly geek suggested I change the power supply. Sure enough that's what it was. I have run into the same problem with a friends computer and a new power supply fixed that too. Hahaha she thought she had ghosts.

December 7, 2012 9:49 AM

On an ATX-type power supply connector (in most desktop type computers), pin 14 is 'power on'. A 'low' on that pin turns on the power supply.

The originating circuitry is, of course, on the motherboard.

On the OTHER end of that is the power supply itself, as mentioned by Rick.

Replacing a power supply is not an expensive option. If you have a name-brand PC, your best option is the same model/PN supply. Other 'one/each' power supplies may operate the machine, but also may give you other problems.

As Leo said, the power strip idea is not an elegant resolution, but it will work.

J. Servis
December 7, 2012 10:32 AM

I was going to say PSU as Rick did. The switch, not much to it. It either works or doesn't.
PSU's are not that difficult to swap out, 15 -30 minutes depending on your mechanical ability & can be purchased at "that auction site" for $30 - $40. plus shipping.

December 7, 2012 12:23 PM

I thought of malware, as has already been mentioned, but I also thought of a Scheduled Task (in the Control Panel). Such as a virus scan or update virus definitions, etc.

There is an option that you can tick in the task that tells Windows to wake up the computer to run the task. I don't know if that refers to just wake from standby, wake from sleep, wake from hibernation, or actually turn the power on. But it wouldn't hurt to check any scheduled tasks.

Just Me
December 7, 2012 1:10 PM

a Fried power button will also shut the system down unexpectedly
if the switch is making contact long enough the start the system it will also do the same and shut the system down whilst you are working

In the power options, properties box (advanced tab)
is a setting:

"When I press the power button on my computer:"

which has the options:
- "Shut Down"
- "Do Nothing"
- "Ask me what to do"
- "Standby"

if hibernation is enabled
then the option
- "Hibernate"
becomes available as a selection also

The default selection is "Shut down"
so a fried power switch that is starting the system up will also trigger this and shut you down unexpectedly

The press & hold for 5 - 10 seconds is an ATX / ACPI specification which bypasses the OS to shut down the system
a short pressing of the button (same press as used for start up)
will trigger the power option event selected in the power properties

so I'm leaning toward this unexpected startup
being a software problem
be it malware: virus / spyware or a legitimate program
The task scheduler is one that can cause your system to do unattended start up

If you look at the properties for any scheduled task there is an option to have the system started to run the task

December 11, 2012 4:27 AM

it is good information for my pc i already solve the problem by the help of u thanks!!!

December 22, 2012 1:00 AM

I love this web site! I appreciate all of the advice offered.Unfortunately, I am disabled and Social Security is not offer people any "extra" money for computer repair bills...etc. The power strip switch works fine for me! I mounted it out-of-sight, yet easily accessible. Definitely not elegant, but effective.
Thank you for the wonderful feedback, everyone!

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