PC won't boot if Sys_fan1 is connected

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Hellcat711

Honorable
Dec 16, 2014
49
0
10,530
Finally narrowed down what was shorting my entire computer, and it is the 4 pin cable from the PSU that fits into the 4 pin sys fan 1 slot. My case fan is connected to the 3 pin pwr fan slot and the PC works fine. The two cables are connected vie a molex plug.

I'm 99% sure that the 4 pin was in place before all this and my computer was fine. Why now and what effect will not having the 4 pin from the PSU plugged in have?
 
Solution
smorizio
dude your lucky the magic smoke has not come out of your mb and cause you to replace it. the cpu fan/cpu 1 and system 1 fan are all powered 12v from the mb and not from the power supply there their to plug in pumps and cpu fans or case fans. the 4 pin power supply molex or floppy connector is 12v out. you use the 4 pin molex to power on case fan controllers.
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smorizio

smorizio

Titan
Jan 22, 2010
30,984
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dude your lucky the magic smoke has not come out of your mb and cause you to replace it. the cpu fan/cpu 1 and system 1 fan are all powered 12v from the mb and not from the power supply there their to plug in pumps and cpu fans or case fans. the 4 pin power supply molex or floppy connector is 12v out. you use the 4 pin molex to power on case fan controllers.
 
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Solution
smorizio

smorizio

Titan
Jan 22, 2010
30,984
9
125,315
when you look at your mb guild there going to be more then one cpu port and more then one fan port. some mb have 3 and 4 pin case fan ports. if there all 3 pin fans and your case fans have 4 pins. you can still use that header you lose pulse with speed sence that on the 4 pin. if you want it neat you can also buy short 3 pin to 4 pin fan cables.
 
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H

Hellcat711

Honorable
Dec 16, 2014
49
0
10,530
Thankyou, the thing works, booted and I'm looking at Windows 10 desktop once again. Couldn't have got this without you :D love this bloody forum. Now I know what definitely not to do :)
 
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M

mbarnes86

Splendid
Sep 16, 2010
3,839
7
26,965
Hi

The only miniture 4 pin connector on a power supply that would fit a fan 4 pin on motherboard is the 3.5" floppy disk power connector ( long obsolete )

As said above only
12 volt atx or eps plug near cpu with 4 or 8 pins and
Atx 24 pin plug
Used to put power into mother board

Only on servers or old or weird motherboards are extra connections from psu to motherboard made
Unless motherboard manual says otherwise

Regards
Mike Barnes
 
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