CPU & Case fan start while computer is turned off

By jade ·
I've got something really weird happening. My computer was custom built with an Asus P4P800-E motherboard. It's run great for the past 20 months. But in the last couple of months I've noticed something bizarre.

In the middle of the night, while the computer is turned off the CPU and case fans start all by themselves. They'll run for a while and then turn themselves off and then repeat the cycle.

The LED lights on the front flash while this is happening. Also, since it's connected to a 4 port KVM switch (via USB) it causes the KVM switch to beep and flash the light for this computer.

One more thing. It seems to be triggered at about the same time each morning (approx 4AM).

Anyone have any ideas about what could be causing this? It's driving me nuts.

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All Answers

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You are getting Power Spikes

by HAL 9000 Moderator In reply to CPU & Case fan start whil ...

Down the Mains when there is a Voltage Drop and this is the cause of the problem.

If you are toward the end of the Mains Power Line or have something that draws a lot of power this will be the cause of the problem. Things like AC units and swimming Pool Filters quite often cause this to happen. The only real cure is to place a UPS between the computer and the mains to prevent this from happening.


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Am using a UPS

by jade In reply to You are getting Power Spi ...

Hi and thanks for the suggestion. But I'm already using a UPS and the computer is plugged directly into it.

I've got 3 other computers also plugged into the same UPS and none of them are doing this.

I'm inclined to think that it may be something peculiar to the motherboard. It's got features like voice prompts at boot, music playing without turning the computer on and so on.

Possibly a BIOS problem? The computer is trying to wake for some reason?

I really don't know.

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not uncommon problem

by dma69593 In reply to Am using a UPS

Yes it does seem weird but I've heard of other peoples computers turning themselves on and off during the night. It seems to be more Asus than others. Have you tried finding out about this on the net? Or asking comp technician?
If you can't solve the problem and your pc seems to be working fine, it's probaly ok to leave it unless you are finding it annoying.
The music playing when the pc is off is weird and a bit freaky. Ghost in the machine?

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Music feature is called "Instant Music"

by Absolutely In reply to not uncommon problem

It is supposed to allow a sort of partial startup, that will only power the CD-ROM drive and the onboard sound(!) so I can play music, but my keyboard isn't triggering this. I guess I need a better PS/2 keyboard to supply the required electrical current, but it doesn't seem worth the bother.

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Remember that with ATX Power Supplies

by HAL 9000 Moderator In reply to Am using a UPS

The 5 Volt rail always has power to it and this is what is used to switch on the computer when you press the On Switch it causes a ripple in that 5 V DC Supply and turns on the PS. So if you have a UPS in place with other computers connected and no problems I would be looking at a PS going bad as an obvious item to look at but as you say that it's turning on about the same time every day the easy solution is to unplug the unit while not in use and then plug it back in when you want it.


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I notice in the specs

by Jacky Howe In reply to CPU & Case fan start whil ...

that it has these extra settings in power management.

Wake-up on modem, mouse, keyboard, LAN, timer and USB

Try disabling them.
Edit: had another play

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