Faulty motherboard or power supply?

cyberpotato

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Dec 28, 2009
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I have an unusual (to me) problem. When I shut down my computer, my chassis fans continue to run. They will continue to run even if I disconnect the power cord. The only way to stop them is to disconnect them from the motherboard. I figure this is either a problem with the motherboard or the power supply, with the MB the most likely culprit, but I'd like to hear some other thoughts before I spend a bunch of money on a replacement. Anyone seen this type of problem before?

Any help appreciated.
 
I have. This occurs only with certain boards and power supplies. Mine has a green light that stays on when the ps is plugged in. Try a different one if it bothers you. You can also disconnect the power supply plug or place your overload protector on top of a table and shut off everything with the trip switch. But then your motherboard battery may run down faster.
 

cyberpotato

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Thanks, Oldie. I have gone so far as to remove the power cable and the fans still run. I'm not a hardware expert, but this leads me to think it is either a capacitor, probably in the power supply, or the battery on the motherboard that is supplying the power to the fans. Either way, I think this indicates a short somewhere, and such a short may cause a complete failure of the motherboard at some point. If my thinking is correct here, I need to replace either the power supply or the MB, but I don't know which is most likely at fault.
 

JackFrost860

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It's a rare feature, but eventually the fans switch off. You may find a setting in the bios to switch the post shutdown cooling feature. It should be under the 'intelligent fan control' section.
 

cyberpotato

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I considered that, but I don't think that's it. It never turns off, even when I remove the power cord, so I'm fairly sure it has to be a fault somewhere. (OK, it would eventually go off without power. I don't think it will violate the 2nd Law of Thermodynamics, after all.)