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Ask HTG: Why Is My Computer Waking Up Prematurely?

Putting your computer to sleep overnight to save energy and resume your work first thing in the morning is a handy trick, but what if your computer wakes itself up early like an energetic toddler? Read on as we help a fellow reader figure out what exactly is waking his PC up.

Dear How-To Geek,

I have a sorta-strange request for help. My computer seems to be waking itself up. Every night I hibernate the computer and then every morning I wake it back up to start working where I left off. That’s how it has been for ages, but lately I’ve been going into my office and my computer is already on and waiting for me to enter my password. I’ve put it into hibernation early a few nights and hung around just to see if it was immediately coming back out of hibernation, but that doesn’t seem to be the case. Some time in the middle of the night, presumably, it just wakes up and sits there idling.

I have absolutely no idea where to begin trouble shooting this or what would even cause it. It didn’t used to happen, it now happens, what can I do? How can I figure out when it’s waking up and how can I stop it from doing so? I’m running Windows 8.1 on a pretty basic office-type desktop machine, nothing too fancy going on. Help!

Sincerely,

Insomniac Computer

Phantom computer problems are always the most frustrating, especially when you’re not even present to see what’s happening. Thankfully Windows has logging/check tools we can use to peek under the hood after the fact to see what’s going on. Although you’re asking about a Windows 8 machine, these tricks will work on older versions of Windows too. When diagnosing a wake up problem like the one you’re experiencing, armor yourself with a dose of patience first. There are a wide range of things that can wake a Windows PC from sleep: scheduled events, mouse/keyboard input, and hardware (like the network card or attached peripherals) so solving the problem is rarely as simple as opening the Control Panel and unchecking a single box.

Let’s start with a little sleuthing in the system logs. Before you spend your time digging through system settings and trying fixes, we want to first establish that the problem is persistent and to answer your question: when is the computer waking up? For that, we’ll turn to Windows Event Viewer, a handy logging tool that will help us see when your computer turned off (be that because it was shut down, put to sleep, or hibernated) and when it woke up. We’ll be using one of our desktop machines as an example machine, but you’ll be able to follow the exact same steps on your machine to do your own sleuthing.

From the Windows Run Dialog, enter eventvwr.msc to launch the Event Viewer. In the left-hand navigation pane, navigate to Event Viewer (Local) -> Windows Logs -> System. There you’ll find a lot of information. Don’t worry, you don’t need to read through or attempt to understand it all, there’s a ton of stuff going on in the log; we’re going to filter it to just the stuff we need to look at.

Right click on the System entry and select Filter Current Log…

In the Filter Current Log dialog box, leave everything in the default setting except the Event sources box. Scroll down within the pull-down menu and check Power-Troubleshooter. This will filter out the hundreds of messages that aren’t relevant to our problem and hone right in on the thing we care about: when the computer is waking up from a hibernation/low-power state.

In the new filtered view, seen above, you can check every time your computer has woken over the duration of the log (which should be hundreds of entries). What you should focus on is the time (did it wake at a time you were at the computer or was it a random middle-of-the-night wake up call?) and what the Wake Source is indicated as in the general details pane.

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If the Wake Source says Power Button, that indicates that the power button on the computer was pressed to wake it up (like you would do first thing in the morning).

If the Wake Source says something like Device – HID-Compliant Mouse (or Keyboard), that indicates the computer is setup so that key presses and mouse movements will wake it. Wake Source: Unknown, as seen here, is a bit more cryptic but at least it tells when the machine was turned back on.

Once you’ve checked the Event Log and you’ve established that there is in fact a pattern of odd computer wake up calls, you can then turn to our handy guide on keeping your computer asleep: How to Prevent Your Computer from Waking Up Accidentally. The guide covers three critical tricks: checking which devices have the capability to wake the computer (using the powercfg command), how to disable the wake ability of those devices (via Device Manager), and how to disable any software-based wake timers (via Power Options).

Between studying the Event Log to understand when (and, if the Wake Source was clear, why) the machine turns back on to using our sleep prevention guide to put a stop to the midnight wake up calls, you’ll have a deep slumbering computer in no time.


Have a pressing tech question? Shoot us an email at ask@howtogeek.com and we’ll do our best to answer it.

Jason Fitzpatrick is warranty-voiding DIYer and all around geek. When he's not documenting mods and hacks he's doing his best to make sure a generation of college students graduate knowing they should put their pants on one leg at a time and go on to greatness, just like Bruce Dickinson. You can follow him on if you'd like.

  • Published 04/24/14