PSU makes a noise, Changing BIOS setting to shutdown on fan failure. Now the computer won't start

Question

This is my scenario:

The PSU is making a whining noise. It's a very high pitch noise, load enough to make it easy to hear it. It had been doing this for a while. I thought that I would buy a new PSU and replace the current one, as soon as possible.

I gave the computer to someone. When I had set it up I thought I'd change some BIOS settings:

1. I turned on the feature which warns if the CPU temperature goes to high and I set it to shutdown the computer if it goes a fair bit higher than the warning. The temperatures (CPU etc) where at nice levels so it was simply a precaution for the future.
2. I turned on the feature which shutdowns the computer if a fan stops working. I suspect that this was a mistake.

After rebooting the computer only starts for 1-2 seconds and then shutdowns. I suspect that it's detecting a broken fan, most likely in the PSU.

I'm not sure if the fan actually is broken, as the PSU is of the silent type which doesn't spin up the fan unless it's necessary. I can't remember if it always started the fan for a while when the power is turned on or not. At least now the fan isn't moving at all until the computer shuts down again.

I have some ideas on what to do:

• Buy a new compatible PSU and plug it in. Since the current one is making that high pitch noise it's most likely at the end of its life anyway. So even if it's not the cause of the computer not booting it's not a waste of money. Still, the computer did work even though the PSU was making a noise. On the other hand, if the PSU breaks it might take other components with it when it goes which would make the ordeal even more expensive.
• Reset the BIOS somehow. I can't get into the BIOS menu as the computer shuts down before that. I think there are two pins on the motherboard I can connect together to reset the BIOS, but I have to check the manual.

What do you think I should do?

Answer 1

You're right, try to find that manual and reset the BIOS. Before that, you could try to hit Esc to stop any memory test, to maybe allow you to get into the BIOS setup after all. But I assume you've tried that as well.

If you ever get into the BIOS again, you'll probably find some screen that shows the current fan speeds. If none claims to be zero, then maybe the BIOS did not find a faulty fan after all, and this is just some bug, like responding to some fans that are not present at all. I think you cannot be sure that a fan in the PSU is indeed not working at all. Save the money for a new PSU; first try to get your computer to boot again!

If you find that manual, then maybe you can also find connectors on your motherboard for additional fans. If you cannot reset the BIOS (which, however, should be possible I guess), then attaching a fan to any non-used connectors may help your computer boot. You could also make sure that the attached fans are actually connected using all pins on the connector. (To measure the actual speed some feedback is required, which I assume needs more than just two wires for the power source.)

I actually doubted the BIOS would know the speed of any fan inside the PSU. But I stand corrected: a comment from Nikhil states that a PSU may be connected to the motherboard to tell it about the fan speed (and temperature?).

EDIT 2: I happened to see a link to How to Reset Your BIOS at Overclocked too far - computer will not boot here on SU.