I've accidentally plug in my fan casing while the pc is shut down(but still connected to wall plug and psu switch is 'ON')

[jvlapple]

Like in the topic, ive accidentally plugged in my fan casing to the Y splitter connected to fan header while the pc is shutdown but didnt turn off the psu switch. Could I do some damage to the MOBO or other component of the pc by doing this? Ive look anywhere all over the internet but couldnt find the answer. Thank you.

[Eigenvektor]

Not really, no. While the PC is turned off, the power supply won't deliver power to anything other than the board's standby power (to detect a power button press).

 

It's a certain risk (also to yourself) because theoretically the power supply could be faulty and deliver power when it shouldn't.

[mariushm]

I don't see any way you'd cause problems to your computer.

 

While the pc is turned off, it only gets 5v stand-by to power the chipset which in turn may power a few usb ports (in case you have a mouse or keyboard and you want computer to turn on by pressing a button on mouse or keyboard)

The connectors for fans have no power, so there's really no way inserting or disconnecting something to affect the computer. Only when you turn on the system, those connectors get power.

 

Even then, the connectors have some built in protections so that you can even add fans while computer runs but you have to be extra careful not to accidentally insert the connector incorrectly (ex jump a pin).

That can cause a short circuit which may cause the power supply to turn itself off in order to protect the computer (and unplugging the mains cable for a few seconds then plugging it back in would reset the power supply and get it working) but most likely instead of this happening, the connector may just overheat and melt or the wire going to the fan may break (as it's thin, it acts like a fuse and the wire overheats and breaks)

So basically even then you won't do permanent damage to the computer.