Computer not booting when system fan plug is connected

[Harry9001]

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 ?

 

[P4-630]

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 ?

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

 

[Jetster]

Bad fan

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

 

[DeathtoGnomes]

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.

 

[Harry9001]

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

 

[P4-630]

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:

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

 

[Caring1]

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?

 

[Bill_Bright]

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.

 

[thebluebumblebee]

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.

 

[Bill_Bright]

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.

 

[thebluebumblebee]

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.

 

[Bill_Bright]

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.

 

[Harry9001]

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 ?

 

[Dethroy]

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.

 

[Mr.Scott]

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......

 

[thebluebumblebee]

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

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

Which looks like this:

 

[Bill_Bright]

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.

 

[Mussels]

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

 

[Harry9001]

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.

 

[dorsetknob]

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

 

[Mr.Scott]

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.

 

[DeathtoGnomes]

Wow, just wow.

 

[Mussels]

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 :/

 

[bencrutz]

dayum

 

[Frick]

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.