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Strange Power(?) Problem

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forgrim

n00b
Joined
Nov 1, 2007
Messages
8
I bought an Antec P180 case back in December of last year, and moved all my components into the case. I had an Enermax 420W powering my AMD 3500+ and various other components (2 HD's, and one DVD-burner, x800 pro, chaintech vnf-250 mb) and ran into an odd problem of if i connected more than one of the case fans, the system would not power on. I tried all the fans individually and the system would power on and the fans would whir all individually, but as soon as i added in another fan, the system just wouldn't boot.

I naturally assumed this was a power problem and bought a Corsair 550VX and painstakingly installed it into the Antec (great case, but seriously, the power supply area is so cramped) and connected everything and wallah. as soon as i connected more than 1 fan, the system wouldn't boot.

I had thought that this was a power supply problem obviously but now i'm wondering. Can a damaged fan suck in so much power that it'll disable the system, or does the motherboard need extremely pure energy or something, i just can't figure it out. Thanks in advance.
 
Is it always the same fan?

If the fan has a short, of course the PSU is going to shut down.
 
I know that if I connect the power supply to two of the fans individually (as in only one of them is hooked up to the PSU at the same time), they spin and the system can boot up, but as soon as I add the other fan in, the system light blinks, but immediately shuts off. (There's a third case fan in the P180 next to the power supply that i'm not 100% sure if it individually works, will try when i get back home). Also to note, when it immediately shuts off, I have to pull the power cord on the back of the PC to try again, or else it won't power up at all, even with the fans disconnected.

I'm not an electrical engineer so I don't understand the concept of how a fan short can systematically disable a system, can you please explain? Thanks.
 
If the fan is indeed shorting, it will allow more current to flow than it or its wires were designed to handle.
This will generate heat and will either burn out the fan / wires or set on fire if the PSU doesnt shut down!
The PSU has protection to prevent it giving out more current than it is designed for and will shut down if max current is exceeded.

This protection only works if the PSU's output capability has been exceeded, not all (apparent) short circuits will trigger the PSU to shut off.
A more Powerful PSU can set fire to a component without shutting down if the fault isnt quite a short circuit and still allows a massive current to flow.

It would be nice if PSU manufacturers allowed the owner to dial in the max current level for it to shut down, maybe in the distant future :)
 
forgrim said:
...when it immediately shuts off, I have to pull the power cord on the back of the PC to try again, or else it won't power up at all, even with the fans disconnected.
Click to expand...

Then you have a short; the PSU is latching into protection mode. Bad fan.
 
Is there a logical reason in that if i test the fans individually (The top fan and the back of the case fan), they work, but as soon as I attach both to the power supply, the system doesn't even boot? I have no idea which fan is bad and so my only option is to send both of them back.

I'll do more extensive tests when I get back home. Is there any threat to damaging my system going back and forth to see which fan is the fan that shuts my system down?
 
I wasnt sure if the problem was down to a single fan or not before.
Are you 100% sure that any 2 of your fans causes the problem and that no single fan causes the PSU to trip?

If so, the fans may have a manufacturing defect/fault that allows an excessive amount of current flow.
This isnt showing up when you run one fan but with 2 is enough to trip the PSU.

As the fans start they effectively present a short circuit before they start moving. With 2 fans, the shorts might be long enough with enough current flow to trip the PSU.
The cure for this is to use different fans.

Can you try 2 other different model/manufacturer fans to see if the same happens?

I would say no that you are unlikely to damage the system but there is a risk.
 
I ran some tests and I could connect two of the three fans and have the system boot up, but as soon as i connected the third (the top one), it wouldn't boot up. I tried the top one with the back one, and the bottom fan, and it would never boot up. the back and bottom together would boot up however, so i've concluded that the top fan is shorting. I decided to RMA it to Antec, and when I unscrewed it, I noticed one of the wires was frayed. Is this a possibile reason why its shorting?

Thanks btw, to Johnny and Nenu for helping me out with this issue, I learned that something as menial as a fan could shut down my system.
 
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