PSU not powering down?

Hi,

I just got a new case+PSU, and it does as follows:

When I plug the power in, the CPU fan starts spinning at full speed and the hard drive powers up. Nothing appears on the monitor until I press the PCs power button - then the computer starts booting and the CPU fan calms down.

It runs fine once I've turned it on and gives no problem when on.

Same problem happens on shutdown. The computer 'turns off', but the CPU fan starts spinning really fast, and the hard drive does not power down.

Is there any way to fix this problem (I'd prefer to fix this as this was the last case of this type that they had in stock) or do I need to return the case for a refund?

Thanks for the help!

Sounds like a short.
check to make sure all standoffs are in the correct holes.
Also, check for any extra or missing.
Check for unused molex or sata power connecters that could be touching the side of the case.

Have you tries a different power cord?
different wall socket?
different circuit?

Wow, this is weird. It might sound stupid, but is there any way to try the PSU on a different motherboard/computer? Wonder if there might be something wrong with the motherboard. Since the CPU fan does not get power directly from the PSU, but from the motherboard.

But the power runs through the motherboard via the PSU.

but that makes sense still mike. If the HDDs and CPU fans are spinning, then it could be a short or a motherboard issue. I suggest pulling your PSU out, and just remounting it. Also Fasten all your motherboard screws as well just to make sure everythings properly grounded.. If it still happens. Try what mike says, and if you have a spare PSU or system, swap something in/out and see if it still happens.

Just a quick update - I disconnected the PSU from everything (ie, not even plugged into the motherboard at all) and as soon as I put the power cord in, the PSU turns on and its fan starts spinning. I also held all the cables in the air, so nothing could be touching the side of the case.

That should not be happening. Is it still mounted in the case? If so, take it out and run the same test. If it still comes on there must be a manf. flaw of some sort causing a short. you need to RMA it

I notice that you did not indicate what kind of PSU you purchased. If the PSU came with the case, you should scrap it and buy a quality PSU.

Hmmm, this recently happend to me. Whenever I shut down my PC the PSU would stay on, I just reinstalled Windows and it worked fine.