Water Cooling CPU Overheat Protection

Hi ALl,

I have a circuit in my computer with a thermal sensor on my cpu, and it basically has a colorful lighting effects for heat of cpu,
I want to run a 2nd program on the arduino board to control a relay once hitting X Temperature...

Basically I want to FORCEFULLY Shutdown (in case of Overheat) such as pump stop etc..

The Idea I have is to route one of these
16, PSU_ON or
8, Power Good
to a relay when relay switches ON, disconnecting that signal wire, thus shutting down.

Ignoring the possible data corruption etc...
I could design a 4 second relay to trigger a shutdown command but computer may hang on shutdown etc..
I am thinking when i'm away I want this to be automatic!

Would you think this is a Safe way to go? I wouldn't hurt the power supply by doing this?

If you want to use an Arduino I would power it using the 5V SB (Stand By) power from the existing PSU. On a 24 pin ATX form factor motherboard connector the PS_ON is held at a logic high using pull-up resistor. Pressing the front panel Start button places a logic low on the PS_ON. Removing the Low or holding the PWR Start button in for about 5 seconds will do a forced shutdown. Given some choices I would bridge the power on button using a transistor like a 2N2222 or any general purpose switching NPN transistor and have your Arduino turn on the transistor at a pre coded temperature.

Ron