using PSU fans as case fans

[matt_ramsey]

Every time I try and use a 12 volt power supply fan as a case fan (by hooking it up to a 12 volt power dongle), they push way less air than when they were in the power supply. why is that? Is there a way I can fix it? I just don't want to go out and spend money on 80mm case fans when I have plenty of fans right here that I know are capable of pushing air. any advice is appreciated!!

[krakerman]

dunno much, but they are probably designed differently. maybe to push straight ahead, or even to push less air since its pushing into the closed psu? thus maybe a case fan has more actual moved ait and a large air of it blowing in. i have no actual idea though ;p

[ROH]

How are you connecting these fan exactly? I stole some 4pin conectors from a few old fans from my older machine and spliced and soldered the wires from two PSU fans into them, and as far as I can tell they are pushing quite a bit of air! they seem to be spinning just as fast as before, and the air they push might even be more then before as they don't have those old cruddy PSU fan holes to try and push air through! :)

If you don't get your connections together they may not be getting quite as much juice as they should. As well if your PSU is starting to reach it's limit you might find it providing less juice to the fans. When you hook them up do your other fans slow down as well? ight be a poor quality PSU? Now I don't know what you have there so if it's a good one sorry. :o

[Warlord2]

are you using the black and yellow wire to hook thim up?

[ROH]

Yes, I am actually! :) No problems sofar!

I don't have any way of testing this to make sure the voltages are correct, but from what I remember them as being compaired to what they are doing now, I'd have to say they are running at peek level.

I've got two 80mm fans connnected this way! both from PSU's that went down and they both run well! Both blowing air into my case!

[batboy]

I've used power supply fans as case fans before, they are no different except there is no connector. If the fan is running significantly slower, than you hooked it up to the 5v wire and not the 12v wire. The standard four wire connectors in a computer has two grounds (usually black) one 12v and one 5v wire. I've seen these wires various colors, but usually the yellow is 12v (but not always). A voltage meter might be handy for this project.

[matt_ramsey]

my psu is a generic 300 watt, and it's just running a little old celeron/gf2mx. But I have tried using many power supplies with many fans, and always the same result- way less air. I will try hooking up to other wires on the dongle- i have been using red and black, since those are the colors of the wires coming off the fans. Thanks for that tip (i am no electronics expert whatsoever).

[The Overclocker]

ther are lots of different 80mm fans, for instace they go from 20 CF to 69CFM, this is quite a large difference, another idea might be that your pus may not be up to the job, i doubt it though.

[Maximus Nickus]

They where probably set up to use a diff voltage in you psu.

[batboy]

The Overclocker is right, 80mm fans come in various CFM ratings. What I meant when I said there was no difference was that the fan should spin as fast and move as much air when used as a case fan as it did as a power supply fan. Obviously, if your power supply you pulled the fan out of was a cheapie, then the fan is probably a cheapie too. You're right about those PS fans usually having red and black wires, but the 12v wire in most 4 wire molex connectors is often yellow (I think).

[donny_paycheck]

Originally posted by batboy
The Overclocker is right, 80mm fans come in various CFM ratings. What I meant when I said there was no difference was that the fan should spin as fast and move as much air when used as a case fan as it did as a power supply fan. Obviously, if your power supply you pulled the fan out of was a cheapie, then the fan is probably a cheapie too. You're right about those PS fans usually having red and black wires, but the 12v wire in most 4 wire molex connectors is often yellow (I think).

I've never seen it anything but yellow, even on older AT PSUs and non-PC PSUs. Must be some kinda industry standard...?:D

[ROH]

Ya, hook them into the yellow and black! that should give you a little more juice! :)

[adamtekh]

i found a nice little jack pot @ school bunch of old mac PSU with panaflo 92mms 13 of them , im useing a couple they puch alot of air , i made the same mistake red and black , its yellow and black :)

[matt_ramsey]

Using the yellow wire instead of red fixed me right up. man i have been stumped over this for like a year and a half now (my fix: use AC fans....). Thanks a lot for your help guys, i knew these fans had it in 'em!

[ROH]

Well the one benefit of running them your way! Long Life expectancy! :)

Glad we could help make those PSU fans do what they are supposed to. Blow lot's of air! :)