Power LED stays on when computer shuts down

By gsimmons30 ·
I have run into the strangest computer problem I have ever encountered in all of my years messing around with computers. The computer is working -- in all respects that I can see. I can go on net, run programs, read and write CDs, execute Windows functions etc. But the front case power LED stays on when the computer is shut down. The mother board is an ABIT IC7-G which I have used to assemble three computers, so it is a motherboard that I am very familiar with. I have another one in the laboratory at this moment, also working just fine, but with the power LED not exhibiting this strange behavior. Both machines are running Windows XP Pro with SP2 installed. I have checked and double checked -- even comparing the plug wires with the one that is not misbehaving -- and can not see where the two are different in any way. Thinking it might be power supply related I swapped out the Thermaltake Pure Power 420w that was in the case with a new Thermaltake Pure Power 480w, which just happens to be the power supply in the IC7-G system that is not misbehaving. Didn't make any difference. I pulled it out of the case and assembled it on the bench, same result, the power LED stays on when the computer is shut down -- not set to standby or hibernate, but a full shutdown. That means it is getting power somehow from the hibernate supply -- but how? While on the bench, I stripped it down to only a graphics card and hard drive -- with no difference.

Given the troubleshooting I have done, it is not the power supply, it is not a case short nor is it case related since when I assemble a computer on the bench I have a momentary ON switch on a short length of wire to turn the computer on and an LED on a similiarly short length of wire to monitor the status of the power.

The computer is definitely not in standby or hibernate mode. Neither moving the mouse nor pressing any combination of keys on the keyboard will cause it to come up. The only way to get it to turn on is to press the start switch after which it goes through a full bootup to come back on line. If I shut down the computer it goes through the normal sequence for shutdown and turns itself off. The power LED stays on as I have said, but there is another even more mystifying thing. It has two optical drives -- a Benq CD/DVD reader and a K-Hypermedia 52x24x52 writer. Each of these drives has an activity LED that flashes green to show activity when the drive is in use. I hadn't noticed before, but the K-Hypermedia LED glows orange when the system is powered down. The LED on the Benq is off when the machine is off. When the machine is turned on, both drive LEDs are off when the drives are not in use. In other words turning the computer off turns the LED on the K-Hypermedia on -- to an orange state instead of the green it shows when in use.

As I mentioned above, I have another computer built on the same ABIT IC7G motherboard in the lab. They both have the same BIOS versions and both have the same two modules of OCZ Platinum series II memory. They differ only in the speed of the Intel Pentium 4 CPUs. I did a line by line compare of the BIOS settings in the two machines and they are set identically. I thought there was some remote possibility a BIOS setting (especially in the power management section) could be the explanation.

I have run out of troubleshooting ideas (for now) on this one. In all of my years of building and maintaining computers I have never encountered anything this inexplicable before. Just goes to show that there is always something new under the sun -- where computers are concerned.

Any ideas. Here is your chance (and I would welcome it) to put me to shame in troubleshooting.

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All Answers

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Bad Motherboard

by TheChas In reply to Power LED stays on when c ...

I'm fairly sure that there is a problem with the power control circuitry on the motherboard.

You should be able to prove this by moving the motherboard between systems.

If you know how to use volt meter, you could check the status of the +5 and +12 for the drives, and just how much voltage is on the power LED.


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Possible reversed polarity??

by mjd420nova In reply to Power LED stays on when c ...

Is it possible that the connector that comes from the LED to the system board is reversed?? I've even seen some with dual color LEDs that will change from red to green and that's only the beginning. You could also check the BIOS setup, some have options for power/hot keys, meaning the power supply never really shuts down, thus the light remains on.

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Motherboard was the culprit

by gsimmons30 In reply to Power LED stays on when c ...

Thanks for the replies. It was the motherboard -- but how I cannot figure out. I measured the 5v bus when the machine was turned on and got 5.124 volts (Fluke DVM). When it was turned off it was reading 4.01 volts. On the good machine the voltage when turned off dropped to a few tenths of a volt as the capacitors slowly discharged. In other words somehow 4 volts was still on the bus when it should have dropped to nominally zero. After I measured these voltages I watched the Power LED on the front of the case carefully and it did dim noticably when the power was turned off. Hadn't noticed that before. Since this was such a mystery, I pulled the motherboard from the working computer and installed it in this system. Took a couple of hours to do, but the computer works fine with the other board -- and the Power LED does go off when the machine shuts down. The surprising thing is that the motherboard that had this problem worked fine in all of the things I did with it. Ran programs, browsed the internet, sent and received e-mails, accessed a thumb drive and read the Compact Flash card from my Nikon camera. You would think the problem would have interferred with something working, but it didn't.

Thanks again. I still can't imagine the nature of the problem, but apparently the VSB keep alive 5 v was being connected to the regular 5 v bus -- through enough impedance to cause the roughly 1 volt voltage drop. I have examined the board under a large bench magnifier and can see nothing suspicious.

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Leakage Path

by TheChas In reply to Motherboard was the culpr ...

While I cannot point you to a specific component, what I suspect was happening, is that there is a leakage path between the 5 volt standby power, and the 5 volt main power.

Even when the power is "off" on an ATX system, there is a low current 5 volt standby power that runs the power control, real-time clock, and other circuits such as wake on LAN.

A solder bridge, or a bad integrated circuit could easily provide a path for the 5 volt standby to reach the 5 volt main power bus.

By the way, if you do find an answer helpful, please rate it as helpful.


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Power LED stays on after shutdown

by shootnhooton In reply to Power LED stays on when c ...

Hi G. Simmons,

I read about your power LED staying on after shut down with great interest as I have exactly the same problem. It is a newly built Win 7 PC using a P6X58D-E motherboard and i7-980x processor and although it appeared to work fine initially, after a minor software problem and a backward windows restore, I got the power LED problem with the occasional blink of the DVD drive indicator thrown in. Interestingly, I can also charge a small mp3 device through a USB port even when it is 'shut down'.

I have tried many things to no avail and I was wondering if you ever found a solution to your problem?

I would be very pleased to hear from you, even if it was not resolved and even more pleased if you discovered the solution!

I know your problem was sometime ago, I just hope this message gets to you.

Kind regards,

John Hooton

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Considering the system is brand new,

by seanferd In reply to Power LED stays on after ...

1) Make sure there are stand-offs where the mobo is secured to the chassis.

2) make sure nothing conductive is laying across the board anywhere.

3) If it is the motherboard itself, have the vendor replace it. (It's new, it should work, right?)

If you did not assemble the machine yourself, have the assembler fix it. (Unless the assembler is your problem in the first place, and doesn't know what he is doing.)

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Key Board LEDs and Mouse Light are on even after Shut-Down

by Anwar Majnu In reply to Power LED stays on after ...

Hi Mr. Hooton,
I have been facing the same problem since July 2010; same thing happened with me; I had UNIBLUE Registry Tweaker, it was giving me some problem, thus I uninstalled it, then I performed System-Restore and BANG ! this weird issue surfaced, I have performed all possible trouble shooting steps; changed power-supply,checked with XP SP2, changed RAM module, tried 'Reverse Polarity', flashed the BIOS with latest update, even took the motherboard out of the cabinet and put it on a table and checked, also did 'Power-Drain' and removed/replaced the battery from the MOBO.
It is now evident that there is a problem in motherboard's 'power-control circuit', it may possible that a capacitor(s) is not properly functioning. I've contacted Intel, they informed me that they are going to change the Motherboard. But, the pertinent question is why it happened. My motherboard is INTEL DG35 EC, OS is Windows 7 Home Premium, I have the same issue. Moreover, I want to add that whenever I switch on(from the UPS), system's power LED turns steady, light in the mouse starts glowing, and the data card's LED also starts blinking, and if I shut-down the system while LEDs on Keyboard turned-on, next time whenever I switch on the UPS, all the LEDs on keyboard become steady, these things happen without pressing the power button on the tower. To the best of my knowledge, nothing should glow except the small green LED on the motherboard; I have talked to my friends, they told me that in certain motherboards, we can make changes (from BIOS Power Option) to make those motherboard work this way, but my motherboard doesn't have that option!
My question is "Do you use any registry tweaker?" If yes "Is it licenced or free or downloaded from third-party website?"

It may happen that the versions of Windows 7 that we are using have BUGs, or it is possible that registry tweaker (or whatever software you are using) is the villain.
Even 8-10 years ago, We used to get virus-attack, that had ability to damage system's hardware but gone are those days; now, Motherboards are immune to these kind of attacks.

So, Sir, Please let me know the name of the software and also let me know the information that I have asked for, if you have any other information, please let me know. Post a reply or contact me at

Thanks & Regard,
Anwar Majnu

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similar problem but on a mac

by robotics In reply to Power LED stays on when c ...

I have a dual quad core mac pro, running 2- 30"apple cinema displays I experienced that when I bought the second display that the power Led on the display would remain on while the computer went through conventional shut down, the funny thing is the original display led turns off has anyone have any ideas? john

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I solved similar problem yesterday

by soldivider In reply to Power LED stays on when c ...

I got a new card reader in my front penal, after I install it, the LED wont off when I turn off Computer. I go through the wires, the reader attached 2 wire, 1 for power( with just black and red wire), 1 attach to Motherboard. I tested it, and found that the power supply is the problem. I unplug the power supply. Bang, It solved.

I recommand you to check your wiring. try unplug some of the device attached and boot your com. see if it will help. :)

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