New Build - Fans are shutting it all down

Laphroaig52

Hello experts

I'm at an early stage in building a new system using a Gigbyte H67N motherboard.

I haven't got the CPU or memory yet but I wired up the PSU and mother board and front panel connectors tonight.

All seems fine (as fine as it can be without a CPU!), front panel switch is working, LEDs on front panel and motherboard are lighting.....

But as soon as I connect the built in enclosure fans, the (Corsair 430W) PSU shuts down. It keeps trying to restart but shuts down again instantly.

So do you think I am in trouble here with a PSU failure or the fans drawing an overcurrent?

Or is it just some weird loading problem due to no CPU etc. on the Motherboard?

Thoughts?

seithon

Sounds more like an issue with grounding maybe?

Laphroaig52

I don't think so.

I put the meter all over the chassis and motherboard and grounding seems good.

It's like the fans are somehow inducing a short.

I played some more and I got to a point where I could connect one fan on low speed but not two and even one fan on high speed caused the shutdown.

Skerries

can you try another psu?

Laphroaig52

Skerries wrote: »

can you try another psu?

I might have to as a last resort. I'd have to rip the PSU out of another build though. Ugh.....the thoughts of it.

game4it70

Flyer28 wrote: »

I might have to as a last resort. I'd have to rip the PSU out of another build though. Ugh.....the thoughts of it.

How are you connecting the fans?
Is it to mobo or direct to psu?

It deffo sounds like a psu problem though if you can run one fan at low rpm but as soon as you increase the power draw it shuts down.

Laphroaig52

game4it70 wrote: »

How are you connecting the fans?
Is it to mobo or direct to psu?

It deffo sounds like a psu problem though if you can run one fan at low rpm but as soon as you increase the power draw it shuts down.

I'm using the fan's Molex connectors and connecting directly to the PSU.

It's weird.

CPU and memory are on the way. I think I'll install them and see if it makes a difference before calling it.

Motherboard may be signalling some kind of power save mode when it detects no CPU...?

Maybe I'm just in denial.........?

game4it70

Would be no harm to rule out the mobo by just having fans only connected to psu with nothing else by using the paperclip method.Here is how or google it more than i did :rolleyes:
http://www.overclock.net/faqs/96712-how-jump-start-power-supply-psu.html

If the psu shuts down with the fans only (trying different combos of fans to rule out a fan causing short) you can at least say its the psu and not mobo or the lack of cpu installed in mobo.

Dublin_Gunner

Or try it without the fans installed and see if the PSU starts.

A lot of PSU's may have a minimum current for operation, and if you're drawing less than the minimum from the 12v rail, the PSU may be auto shutting down.

Wait until you have the full rig together (or at the very least CPU & Ram installed on the mobo) and try it again, with, and without the fans.

Personally, I never turn the PSU on until I have the rig built..

jme2010

Dublin_Gunner wrote: »

Personally, I never turn the PSU on until I have the rig built..

This.

I used to do that when I was buiding a frankenstien of a yoke. "I just want to see if it will boot with no ram or HDD or Mobo"
But not with any good components in my rig. You may fry everything! Just wait untill you get your cpu.....off ebay?

game4it70

In my opinion the psu should be able to run even one fan without having to shut down.
I have used a few psu's with only a pump conected while leak testing a wc loop.They all seem to run even with very low power draw.

Dublin_Gunner

game4it70 wrote: »

In my opinion the psu should be able to run even one fan without having to shut down.
I have used a few psu's with only a pump conected while leak testing a wc loop.They all seem to run even with very low power draw.

Yes, but as a safety feature, some PSU's have an auto shutdown if a minimum power draw isn't reached.

Remember, an ATX power supply is designed for one reason - to run a PC.

Nearly all switching power supplies require a minimum power draw on each voltage rail for stable output. If this isn't reached, the PSU can turn itself off.

Also, this could be the case that the motherboard is not sending the 'power on' signal back to the PSU (as there's no CPU etc installed) and the PSU is auto-switching off.

But, as the OP has stated it powers onm when only the mobo is connected, but not when the fans are, I would have the hedge my bets that its a low 12v rail power draw causing the issue.

I know the newer ATX 2.3 spec reduced the minimum load on the 12v rail. Now saying this, I think there may also be a requirement for minimum load on the 5v rail, of around 2A, so if there's somethign drawing less than this, it could cause it to power off.

You could try disconnecting everything from the motherboard, and run only the fans by shorting the PSU to start-up.

The main thing is, if it doesn't work when you have most/all components installed, then you have an issue.

It could also, as someone pointed out earlier, be something as simple as a fan being shorted or something.

game4it70

Dublin_Gunner wrote: »

Yes, but as a safety feature, some PSU's have an auto shutdown if a minimum power draw isn't reached.

Remember, an ATX power supply is designed for one reason - to run a PC.

Nearly all switching power supplies require a minimum power draw on each voltage rail for stable output. If this isn't reached, the PSU can turn itself off.

Also, this could be the case that the motherboard is not sending the 'power on' signal back to the PSU (as there's no CPU etc installed) and the PSU is auto-switching off.

But, as the OP has stated it powers onm when only the mobo is connected, but not when the fans are, I would have the hedge my bets that its a low 12v rail power draw causing the issue.

I know the newer ATX 2.3 spec reduced the minimum load on the 12v rail. Now saying this, I think there may also be a requirement for minimum load on the 5v rail, of around 2A, so if there's somethign drawing less than this, it could cause it to power off.

You could try disconnecting everything from the motherboard, and run only the fans by shorting the PSU to start-up.

The main thing is, if it doesn't work when you have most/all components installed, then you have an issue.

It could also, as someone pointed out earlier, be something as simple as a fan being shorted or something.

I dont disagree with you but the psu's i've used work fine with minimum power draw.
Hopefully its just a bad fan as much easier to replace.

Serephucus

Can't say much, but of the three PSUs I've used - Tt Thoughpower 1200W, TX650, no-name 500W - they all ran fine with only a pump connected over molex.

Laphroaig52

Well, just to bring some closure here.......

CPU and memory installed and the problem disappeared.

Everything is hummming (nice and quietly) now.
I ran both fans on high for a few hours before installing the OS and it's all very smooth.

Win 7 installed now and she's still very stable.

Thanks to all that responded. It looks like the PSU is smarter (or stupider?) than I had thought!