# Computer not booting when system fan plug is connected



## Harry9001 (Jul 30, 2016)

Hi,
So i just got a new PSU for my old build and surprisingly when i connect the 4pin plug for the system fan, pc doesnt boot!

On removing just this one plug, it boots 

Why is this happening ? 
For specs, check my profile, its fully updated.

PS guys if i leave the system fan(dont attach it) what will happen ?


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## P4-630 (Jul 30, 2016)

Harry9001 said:


> Hi,
> So i just got a new PSU for my old build and surprisingly when i connect the 4pin plug for the system fan, pc doesnt boot!
> 
> On removing just this one plug, it boots
> ...



What if you connect the system fan to another system fan header?
Motherboards nowadays have more than one system fan headers.


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## Jetster (Jul 30, 2016)

Bad fan

But go into the bios and change the fan speed settings. See if that helps


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## DeathtoGnomes (Jul 30, 2016)

First try a different fan, maybe a 3-pin.
Although the system fan header has a 4 pin, it might only accept 3 pin fans. There are settings in the BIOS specifically for the system fan, for which header idk, it might have one for each header, just make sure its not disabled or off.


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## Harry9001 (Jul 30, 2016)

No guys Im not talking about any external fan. 
My gigabyte mobo has 4 pins coming out of it, next to those pins is written "sys_Fan".
When I connect my mobo's connector on those pins, pc doesn't boot.

Whereas in my old psu i did the same and the pc always booted


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## P4-630 (Jul 30, 2016)

Harry9001 said:


> No guys Im not talking about any external fan.
> My gigabyte mobo has 4 pins coming out of it, next to those pins is written "sys_Fan".
> When I connect my mobo's connector on those pins, pc doesn't boot.
> 
> Whereas in my old psu i did the same and the pc always booted



But you are connecting a fan to that "sys_fan" connector aren't you?

I don't get this part:


Harry9001 said:


> When I connect my mobo's connector on those pins, pc doesn't boot.


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## Caring1 (Jul 30, 2016)

Harry9001 said:


> No guys Im not talking about any external fan.
> My gigabyte mobo has 4 pins coming out of it, next to those pins is written "sys_Fan".
> When I connect my mobo's connector on those pins, pc doesn't boot.
> 
> Whereas in my old psu i did the same and the pc always booted


Are you talking about the 4 pin ATX connector for the CPU?


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## Bill_Bright (Jul 30, 2016)

Harry9001 said:


> So i just got a new PSU
> My gigabyte mobo has 4 pins coming out of it, next to those pins is written "sys_Fan".
> When I connect my mobo's connector on those pins, pc doesn't boot.


What?

*You don't connect your power supply to those pins!* Is that what you are doing? If so, you might just destroy your motherboard!

You connect the system fan (typically the chipset fan) to the pins labeled Sys_fan. Those pins deliver power to fan. Those pins get power through the motherboard already.


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## thebluebumblebee (Jul 30, 2016)

Caring1 said:


> Are you talking about the 4 pin ATX connector for the CPU?


Your PSU comes with a 4+4 pin ATX/EPS12V CPU power connector.  Make sure you're using the correct set.  If it took a lot of force to plug it in, that might indicate that you're using the wrong set of 4.  And/or in the wrong orientation.


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## Bill_Bright (Jul 30, 2016)

I agree with thebluebumblebee but again, you do NOT connect any cable from the power supply to any header on the motherboard labeled "fan" - that includes "Sys_fan" which is what the OP referred to.


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## thebluebumblebee (Jul 30, 2016)

Bill_Bright said:


> I agree with thebluebumblebee but again, you do NOT connect any cable from the power supply to any header on the motherboard labeled "fan" - that includes "Sys_fan" which is what the OP referred to.


The SYS_FAN, CPU_FAN and 4 pin ATX/EPS12V CPU power connector are bunched together on his system.  SYS_FAN may be all he's able to read while it's in the case.


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## Bill_Bright (Jul 30, 2016)

thebluebumblebee said:


> The SYS_FAN, CPU_FAN and 4 pin ATX/EPS12V CPU power connector are bunched together on his system. SYS_FAN may be all he's able to read while it's in the case.


Excellent point but all the more reason to ensure he is not connecting a power cable the fan header. I note the 4-pin ATX connector has the pins arranged in a square and is typically a socket. Fan headers are "headers" that is, typically just pins sticking up and in the case of fans the pins are arranged 3 or 4 in a line, not a square.

Plus (I hate to assume, but...) assuming the motherboard in question is the one listed in his System Specs, as seen here, as you noted the 2 fan headers and the 4-pin ATX connector are clustered together, but are clearly labeled.

So before assuming anything else, I think we need clarification from the OP.


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## Harry9001 (Jul 30, 2016)

Im myself confused after reading all the answers lol
Billbright has got it right, im talking about 4 pin lines under which it reads sys_fan

You know like for attaching front speakers there are pins emerging out of the mobo, just like it sys_fan pins are there.

While using my old psu, i use to connect the '4 pin taker' plug( ) to those sys_fan pins and everything use to work flawlessly but now on doing the same it doesn't :/

But i left those pins undisturbed and used the PC for few hours without any problem.

If they aren't meant to be attached to their respective connector from the PSU, then i wonder how my previous psu worked fine ?


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## Dethroy (Jul 30, 2016)

Only the MoBo itself and the CPU need power from the PSU. Then the MoBo powers the sys_fan and the other fan headers all by itself - do not connect your PSU to any of those headers.


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## Mr.Scott (Jul 30, 2016)

> While using my old psu, i use to connect the '4 pin taker' plug( ) to those sys_fan pins and everything use to work flawlessly but now on doing the same it doesn't :/



Don't even tell me that you're connecting a FDD power connector to that fan header. Oy......


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## thebluebumblebee (Jul 30, 2016)

The fan header is 4 pins in a row.  The 4 pin ATX/EPS12V CPU power connector is 2x2, or square.  Like this:





But your PSU comes with a 4+4 pin ATX/EPS12V CPU power connector that looks like this:




Can you see how they are "keyed"?  You want to use the one from the pair that's keyed like the single one above


Mr.Scott said:


> Don't even tell me that you're connecting a FDD power connector to that fan header. Oy......


Which looks like this:


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## Bill_Bright (Jul 31, 2016)

Dethroy said:


> Only the MoBo itself and the CPU need power from the PSU.


Well, and many graphics cards, and of course, drives. And you can power case fans directly from the PSU too, but you won't get any monitoring or automatic speed control that way.


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## Mussels (Jul 31, 2016)

please take pictures of what you're plugging in, and where you're plugging it in.


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## Harry9001 (Jul 31, 2016)

The last pic attached by @mrbluebumblebee is the connector I I'm talking about and the pins that emerge from the mobo are the perfect fit for it.


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## dorsetknob (Jul 31, 2016)

As Said by others
DO NOT CONNECT ANY Cable from your PSU to the sys header pins
POWER FROM YOUR PSU TO THE CORRECT MOTHERBOARD (atx 20+4   AND CPU 4 ) CONNECTORS

YOUR FANS   TAKE POWER FROM THE MOTHERBOARD   NOT YOUR PSU

caps because you need to take notice of this


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## Mr.Scott (Jul 31, 2016)

Harry9001 said:


> The last pic attached by @mrbluebumblebee is the connector I I'm talking about and the pins that emerge from the mobo are the perfect fit for it.


That doesn't mean you just blindly plug it in there.
Jesus.
You're lucky you still have a running rig.


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## DeathtoGnomes (Aug 1, 2016)

Wow, just wow.


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## Mussels (Aug 1, 2016)

heres a pic of the fan connector on your motherboard, and yeah if you jammed a floppy power cable onto that you're lucky you didn't start a fire :/


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## bencrutz (Aug 1, 2016)

dayum


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## Frick (Aug 1, 2016)

Harry9001 said:


> The last pic attached by @mrbluebumblebee is the connector I I'm talking about and the pins that emerge from the mobo are the perfect fit for it.



It's not even 8 in the morning and already my day has been made. 

Attach a fan to it and see if it works. If it doesn't, you've killed something.


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## Mussels (Aug 1, 2016)

In his defence, very few cables inside a PC fit where they are not supposed to - a 4 pin PWM fan connector and a 4 pin floppy power connector can definitely look similar to a beginner - especially if they've never built a PC that actually had a floppy drive!


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## Caring1 (Aug 1, 2016)

Some of the early AT PSU's had the 4 pin Floppy connector and another for something else, not that I can remember or ever used it.


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## Harry9001 (Aug 1, 2016)

lol, whew guess that was a close call 

Thanks for the help guys, and next time will remember not to attach things i don't know about


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## Mr.Scott (Aug 1, 2016)

Mussels said:


> In his defence, very few cables inside a PC fit where they are not supposed to - a 4 pin PWM fan connector and a 4 pin floppy power connector can definitely look similar to a beginner - especially if they've never built a PC that actually had a floppy drive!


They do make manuals for a reason you know.


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## Harry9001 (Aug 2, 2016)

Mr.Scott said:


> They do make manuals for a reason you know.



I did really both manuals, the mobo one doesn't say much and the psu one is kind of informative.
But i didn't read anywhere that i shouldnt connect the psu connector on those 4 sys_fan pins


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## Mussels (Aug 2, 2016)

Harry9001 said:


> I did really both manuals, the mobo one doesn't say much and the psu one is kind of informative.
> But i didn't read anywhere that i shouldnt connect the psu connector on those 4 sys_fan pins



dont feel bad. We may all know better, but we've all made hilarious mistakes in the past too. At least nothing caught fire and the system still works afterwards.


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## eidairaman1 (Aug 4, 2016)

Harry9001 said:


> The last pic attached by @mrbluebumblebee is the connector I I'm talking about and the pins that emerge from the mobo are the perfect fit for it.


That's a floppy disk drive connector, that does not hook up to the motherboard.


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## dorsetknob (Aug 4, 2016)

Mussels said:


> In his defence,


he is probably to young to have seen a Floppy and its PSU power connector
( he was probably wearing Diapers when they were last mainstream fittings in PC's )

I have an ATi AIW Radon 9800se that Requires a floppy power connection to power it


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## rtwjunkie (Aug 4, 2016)

Harry9001 said:


> lol, whew guess that was a close call
> 
> Thanks for the help guys, and next time will remember not to attach things i don't know about



LOL, everyone here has done dumb or accidentally funny stuff with their PC.    Just chalk it up to learning.


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## Harry9001 (Aug 4, 2016)

dorsetknob said:


> he is probably to young to have seen a Floppy and its PSU power connector
> ( he was probably wearing Diapers when they were last mainstream fittings in PC's )
> 
> I have an ATi AIW Radon 9800se that Requires a floppy power connection to power it



Sorry dude but you're wrong, I've seen lot of ancient tech.
Including floppy disks, I even have a few working ones, including a Mitsumi one.
I also have a Pentium II processor and its Asus mobo + I have a pentium III too 

But yeah I guess this just makes it worse that I didn't know which wire was supposed to go where


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## dorsetknob (Aug 4, 2016)

Harry9001 said:


> Sorry dude but you're wrong, I've seen lot of ancient tech.
> Including floppy disks, I even have a few working ones, including a Mitsumi one.



In that case its hard to fathom why you would put  the Floppy power connector to a sensor point/fan connector on a motherboard Since you knew it was ................for a floppy drive

Still at least you did not bork anything


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## Harry9001 (Aug 4, 2016)

dorsetknob said:


> In that case its hard to fathom why you would put  the Floppy power connector to a sensor point/fan connector on a motherboard Since you knew it was ................for a floppy drive
> 
> Still at least you did not bork anything



Yep and I thank god for that, whew !


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## eidairaman1 (Aug 4, 2016)

dorsetknob said:


> he is probably to young to have seen a Floppy and its PSU power connector
> ( he was probably wearing Diapers when they were last mainstream fittings in PC's )
> 
> I have an ATi AIW Radon 9800se that Requires a floppy power connection to power it



It came with the standard molex adapter, do not try to remove that adapter (did that once and killed a card)


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## dorsetknob (Aug 4, 2016)

eidairaman1 said:


> It came with the standard molex adapter, do not try to remove that adapter (did that once and killed a card)


No it came with same power connector as a 3 1/2" Floppy drive >>>>not the Same as standard molex
Ps it is a powercolor AIW 9800 se
google pic  and in top right is white power connector






That my dear Sir   is not what people refer to as standard molex

and this is the power connector  same as floppy drive


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## Vayra86 (Aug 4, 2016)

Thread made my day  

Still glad no animals were hurt, nor PC's, but I did have a good laugh ^^


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## Caring1 (Aug 5, 2016)

dorsetknob said:


> No it came with same power connector as a 3 1/2" Floppy drive >>>>not the Same as standard molex
> Ps it is a powercolor AIW 9800 se
> google pic  and in top right is white power connector


Never mind, I was going to ask if that card still worked with the resistor missing beside the power connector, then noticed it's a Google pic.


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## dorsetknob (Aug 5, 2016)

Yes My Card is still fully working but in storage in original packaging with all accessorys

Its Analog TV so no tv signals in UK  for it


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## INSTG8R (Aug 5, 2016)

dorsetknob said:


> No it came with same power connector as a 3 1/2" Floppy drive >>>>not the Same as standard molex
> Ps it is a powercolor AIW 9800 se
> google pic  and in top right is white power connector
> 
> ...


Wow that brings back memories I had one too I passed it along but I still have the remote and dongle somewhere.


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## eidairaman1 (Aug 5, 2016)

dorsetknob said:


> No it came with same power connector as a 3 1/2" Floppy drive >>>>not the Same as standard molex
> Ps it is a powercolor AIW 9800 se
> google pic  and in top right is white power connector
> 
> ...


Dorset I know about the connector on the card itself however the card had a pig tail that was attached to it, it was floppy to card side but molex to the power supply.


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## dorsetknob (Aug 5, 2016)

eidairaman1 said:


> Dorset I know about the connector on the card itself however the card had a pig tail that was attached to it, it was floppy to card side but molex to the power supply.



mine never came with that cable ( not listed on box as an included component )
Bought it new as well £139.99 on 16 October 2004 )
Had to as new Motherboard was AGP4 / 8 only and my Voodo 3500 TV was AGP2


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## eidairaman1 (Aug 5, 2016)

dorsetknob said:


> mine never came with that cable ( not listed on box as an included component )
> Bought it new as well
> Had to as new Motherboard was AGP4 / 8 only and my Voodo 3500 TV was AGP2



Perhaps the SE didnt need it, I had 2 ATi non 3rd party badge AIW cards, 9700 Pro-Accidently broke it trying to remove the pig tail-got replaced by a 9800 Pro- both had the pig tail which could not be removed.


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## 95Viper (Aug 5, 2016)

dorsetknob said:


> Its Analog TV so no tv signals in UK for it



Yep, I got an All In Wonder packed away, too.  If I remember, it, also, had a radio tuner, too.
I stop using it when the analog TV went digital.
Never had a problem with it...  I used to like watching some TV while surfing the web or doing other work.


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## dorsetknob (Aug 5, 2016)

eidairaman1 said:


> Perhaps the SE didnt need it


It need external power ( from PSU via spare Floppy power connector or PC did not Boot and pc speaker screamed Error bleep)


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## eidairaman1 (Aug 5, 2016)

dorsetknob said:


> It need external power ( from PSU via spare Floppy power connector or PC did not Boot and pc speaker screamed Error bleep)



Yeah what i meant was the pro boards needed the voltages from the molex and the se only needed it from the floppy.


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## dorsetknob (Aug 5, 2016)

Got 2   the above card and a hercules AIW 7500   ( does not need external power )
this one also still working
no Original box or packaging as i acquired it used
neither of mine had the FM Radio Tuner 



eidairaman1 said:


> Yeah what i meant was the pro boards needed the voltages from the molex and the se only needed it from the floppy.


The Pro had 8 pixel pipelines as std and the Se had 4 pixel pipelines as std
My SE drew the limit for power  ( the card connector got rather Warm )
it also had the softmod for the Extra pipes hence the getting warm with the Extra power draw needed for the softmod


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## Mr.Scott (Aug 5, 2016)

eidairaman1 said:


> Yeah what i meant was the pro boards needed the voltages from the molex and the se only needed it from the floppy.


  They are exactly the same voltages. Only the connector is different.


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## dorsetknob (Aug 5, 2016)

Think he meant power Draw as i mentioned in previous post ( was editing when you posted  )


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