I currently have a 330 watt PSU for my computer. I am, within the next two weeks, going to add a water cooling system. This includes an 80 watt peltier, pump, and six 80mm fans. To be safe, I would like to use a second PSU to power the cooling system parts (it is an old 230 watt Dell ATX PSU). The problem is how to turn the PSU on when it won't be hooked up to my mobo. I can plug the PSU into the wall, but no power will go out through the molex cables. I think I have to short two wires that would normally be connected to the mobo, but I'm not sure which ones. Any help would be appreciated. The PSU part no. is: PS-5231-1
Thanx
Full Version: How To Turn On Psu W/o A Mobo
got to compusa and pick up either an compusa or antec brand power suply tester. they allow you to do just what you're asking for (we used em to light up cases without mobos in them).
or take a short leinth of wire and connect the Green wire in the ATX power connector with any black wire on the ATX connector
Yeah what Smeghead009 said, works great. Our technicians at the store do it as a cheap solution to fans, they run case fans taped to the desk to create some airflow. 
The green and grey wires are what turn the PSU on and off. I connected a switch to an old one of mine and powerd an old car amp for fun. Great toys!
Thanx guys! I would have thought it would have been harder than that.
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they run case fans taped to the desk to create some airflow
lol. I would have never thought of that.
Definately green and "black" and here's a how to if you have enough space or a full tower and you want 2 PSU that starts at power on instead of spending good cash for a 500w when 2 inexpensive 350 makes 700w 
i've been using it for more than a year now a 400w for mobo and drives and a 350 for lights and mods
http://www.speedy3d.com/articles/case_mod_..._p3/index.shtml
i've been using it for more than a year now a 400w for mobo and drives and a 350 for lights and mods
http://www.speedy3d.com/articles/case_mod_..._p3/index.shtml
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A typical 250w power supply is able to put out 10amps at 12v. This means that out of 250w total, only about 120w is available through 12v (amps x volts = watts). This is exactly the reason why you can't plug a 120w peltier on a 250w power supply. When buying a bigger power supply, make sure it gives you enough power at 12v. The 300w power supply I have only gives 10amps at 12v, just like my 250w. The additional 50w is available for the 5v and 3.3v lines so it does not help me at all. Other 300w power supplies will give 12amps at 12v. The biggest power supply I have seen was rated at 450w and could supply 16amps at 12v, this gives you 192w of power at 12v but will cost you over 100$. What you could do instead is buy two cheap 250w power supplies and link them; this would give you about 240w of power at 12v for under $50. As you can see, multiple smaller power supplies will give you more power for less money.
Ok, I would like to get a peltier pad for my cpu. After reading this I decided it would cost much less to go with the two PSU design. The question I have is on how to wire the peltier's two wires, + and -, to dual PSUs. I know the two wires on the peltier are rated high enough to carry the 156 watts needed, but will one molex connector be enough to carry the 156 watts (12 volts only). Any recomendations on how to wire them up? I need to take the 12v + and a ground from two power supplies and transfer the power to the peltier's + and - wires. How? Any comments are welcome.
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