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Faulty motherboard or power supply?

Last response: in Motherboards
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June 17, 2011 3:56:41 PM

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.
a c 435 V Motherboard
a b ) Power supply
June 17, 2011 4:53:45 PM

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.
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June 17, 2011 7:38:09 PM

o1die said:
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.


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.
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a c 717 V Motherboard
a b ) Power supply
June 17, 2011 7:51:09 PM

Most of the time this is either a bad PSU or bad connection to the PSU, Reseat the 24-pin and if that fails 9/10 it's the PSU.
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June 17, 2011 10:03:12 PM

jaquith said:
Most of the time this is either a bad PSU or bad connection to the PSU, Reseat the 24-pin and if that fails 9/10 it's the PSU.


Thanks, jaquith!
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June 18, 2011 8:04:14 AM

cyberpotato said:
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.


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.
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June 18, 2011 7:05:24 PM

JackFrost860 said:
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.


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.)
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a c 717 V Motherboard
a b ) Power supply
June 18, 2011 7:29:50 PM

Yes it would be ni$e to find a perpetual machine :) 
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June 18, 2011 8:20:39 PM

jaquith said:
Yes it would be ni$e to find a perpetual machine :) 


:) 
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June 25, 2011 5:12:08 PM

Best answer selected by cyberpotato.
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