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System won't boot with Chassis fans hooked up to mobo

Last response: in Motherboards
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September 16, 2010 4:49:51 PM

Hey Guys,

I have an Asus SLI Mobo (M4N98TD EVO), and I am trying to hook up my case fans to the board so my computer will recognize them with fan control software. I have 1 small chassis fan at the back with a small 3-pin connector attached directly to the CHA2_FAN on the motherboard and it is recognized by the software - so that's good.

I have two larger chassis fans with LEDs (Top & Front of Chassis) hooked up directly to the PSU through one cable that has three of those large 4-pin connectors (for fans), and a small 4-pin connector on the end. The fans work great, however they are not recognized since they are connected directly to PSU.

Now when I attempt to attach the 4-pin connector cable (that contains both fans) to the motherboard, the system won't turn on (blue LED light flickers and then turns off).

Not sure what the problem is, but as soon as unhook the small 4-pin cable from the motherboard, the system boots fine.

Any ideas? I'd love to have these larger fans recognized by my computer, but the system just won't turn on when I have them connected to the motherboard. Thanks for your help.

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a b V Motherboard
September 16, 2010 7:31:58 PM

WOAH! DO NOT DO THAT!!

When you say large 4-pin, you are talking about these right:
http://en.wikipedia.org/wiki/File:Molex_female_connecto...

And the small 4-pin looks like this:
http://img.tomshardware.com/us/2007/08/09/pc_power_supp...

Yeah, those are all power cables.

That small connector on the end with 4-holes is a POWER port for a floppy drive. Your computer won't boot because you are probably shorting-out the motherboard and the power supply is going into a fail-safe mode.

If those are the only cables your fans connect with, then you cannot monitor them, they don't have the necessary sensors and connectors.
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September 16, 2010 8:17:18 PM

Oh wow, ok thank you! I won't do it anymore. Do you think I damaged anything? Everything seems to be fine...

Thanks for the help though!
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September 16, 2010 8:17:49 PM

Best answer selected by gamble85.
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a b V Motherboard
September 16, 2010 8:27:10 PM

If nothing smoked, and it seems to run fine, I'd say you got lucky. Power Supplies have built-in protection to prevent damage in the case of things being shorted out. If you had shorted your CPU, Memory, or something on the board, you would probably know it by now.

If you want to be sure, run memtest86+ and a Prime95 "torture test". If these don't register any issues, you are probably safe.
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