[solved] Weird problem - computer switching back on after shutdown

[Stu]

Got a bit of a weird one here. About a month ago I did a job for a guy with an old Compaq Presario. He had been getting error messages about overheating and the computer was freezing. He asked me to give it a good cleaning internally and install a case fan to keep temps down. This I did and everything seemed rosy.

He has called back to say ever since I did the job, when he switches the machine off, it switches itself back on again. I have been back to check for myself, and sure enough, upon clicking Start --> Shutdown (it's Win XP SP2) the machine shuts down as normal and powers off. The IDE and power LEDs also go off. Then, after a seemingly random amount of time, the machine will power back on and boot as normal. This typically occured within ten seconds of powering off, but the longest I timed was 30 seconds. The only way to get the machine to stay off is to press the power button as it is booting again.

This one has got me stumped. I have checked the obvious, like making sure he is not pressing restart, disabling automatic restart on system error and checking the resume on loss of AC power in the BIOS settings, but that is disabled. Also checked event viewer logs which look normal. Had a delve inside the machine and all appears normal and the power button seems OK.

Any ideas before I call a priest?

 

[Maddiebeagle]

Is there a wake on LAN, or wake on ring option anywhere in the BIOS?

You can also try removing any USB devices from the PC (printers, mice, keyboards, external drives)
Unplug the phone line or ethernet cable, too.

"Old compaq" = how old??? maybe try replacing the battery (CR2032 or whatever they are)

That is a weird one, good luck!

 

[Stu]

Is there a wake on LAN, or wake on ring option anywhere in the BIOS?

You can also try removing any USB devices from the PC (printers, mice, keyboards, external drives)
Unplug the phone line or ethernet cable, too.

"Old compaq" = how old??? maybe try replacing the battery (CR2032 or whatever they are)

That is a weird one, good luck!

Will check the 'wake on' options next time I visit. I'm pretty sure they were in the BIOS somewhere.

The machine I believe is around five years old (2003ish). Is there a way a failing/failed CMOS battery would cause this behaviour?

 

[nonchalant]

Sounds like a problem PSU. The only way to really find out is to swap it out and see if it still does it. Perhaps also reset BIOS to default settings to ensure somethings not been turned on in there.

 

[Jory]

I have a 466 Celeron machine that does the same thing, but only more consistent with it's power on times. I use it for a home server so the behavior was desirable and I never bothered to figure it out.

Given the random about of time it stays shutdown you can most likely rule out any software problems. Since it's most likely a hardware issue and you were messing around in the case I'd first check all the connections starting with the power button jumpers. If they're shorted out in some way it could possibly think the power button is being pushed.

Another likely scenario is that all his rebooting possibly killed the power supply. I've seen it happen before were a machine that's randomly rebooting all the time will kill an old power supply. After you check the wake on lan, etc try swapping the power supply and seeing if it makes a difference.

If it's still happening after that chalk it up to ghosts or an electrical problem you probably won't be able to troubleshoot.

 

[ServingOnlineSeniors]

Had same problem! If we unplugged network cable, shut down fine. Turned out to be in BIOS settings. Good Luck!

 

[gunslinger]

Sounds like to me its the wake on LAN option in the BIOS also. That would be what I would check first If I were you sense its the easy fix.

 

[Stu]

Thanks for the replies all.

I went back to the client today and tested the PSU. It checked out fine, but I swapped it out anyway. The problem remained.

So I had another look through the BIOS settings, and there buried deep within it, and in an entirely different section to the power options I must add, was an option to 'wake on PDE events' which was set to enabled. Now I'm not 100% what the middle letter was, but I think it was a D. I took the E to mean Ethernet. I disabled this option and the problem has gone away.

The client had added a router to his setup not long after I did the original job. I guess this should have served as a clue to me.

Many thanks for everyone's help and useful suggestions.

Stu

 

[generalj]

It was probably wake on PXE or PXE Boot. Which stands for Preboot Execution Environment. Its a pretty cool feature and can be used to do some amazing things. I used it a lot at comcast to automate imaging the computers remotely and on a schedule. really cool. Also if you have a look at LinuxMCE project it uses it so you can have a TV in other room boot up to your LinuxMCE server via PXE and get all the settings you have set up on it. Pretty cool. just FYI

 

[Bryce W]

Definitely sounds like network traffic was waking the computer up. Glad you found it