why will gpu fan not run in reverse

[semajjames]

hi

i wanted to reverse the direction of my gpu fan so i changed around the black and red wires that feed it

i was expecting the fan to run in the opposite direction but it did not do that

in fact it did not run in any direction

so i had to change them back

why is this ??

cheers

 

[Jay794]

Firstly, is this a windup? Changing the wires won't work because one is - and the other is + it won't work. Secondly, why do you want to run it backwards anyway?

 

[Orcvader]

Just flip the fan around? But yes, why do you want to run it in the opposite direction?

 

[reflux]

You're aware that fan blades are designed to push air in one way only, right?

 

[numatic.nathan]

You're aware that fan blades are designed to push air in one way only, right?

This.

 

[semajjames]

ok i thought changing the wires would change direction

may be i need to check my theory on dc motors


i wanted to change the way it ran because

at the moment the gpu fan is pulling air from outside the box and exausting the hot air into the box

i wanted it to pull air from inside the box and push hot air out
this is because if it pulled air from inside it would be getting cool air because of the position of the fan is close to the box main air in

but if there no way to change fan direction + fan physice would not work in reverse the i am best keep it the way it is

thanks

 

[eyetrip]

Step away from the computer...

 

[Jay794]

Step away from the computer...

+1

Hope he's not going to try and watercooler it with the aid of a fishtank

 

[semajjames]

+1

Hope he's not going to try and watercooler it with the aid of a fishtank

lol

no that would not work for sure because my fish tank has no fish or water only land snails and they move too slow to cool a pc ,,,,,

 

[Tealc]

why is this ??

Because brushless DC fans can only go in one direction. Brushless fans work with a circuit board that knows basically where the magnets are at any time, and know which one to switch on and which to switch off. Having the wrong voltage, in this case -12v would not power the circuitry correctly. Brushless fans are quieter because they have less contact between parts and rely more purely on electromagnetism to drive the rotor around. They last longer, are more efficient and cleaner.

Brushed fans can go either way by reversing polarity but they make more noise as the brushes are in contact with the commutator shaft of the motor at all times. It is this that transfers energy to the motor shaft itself and causes the magnetic field. Brushed fans tend to have sparking too from the contact. Examples would be a power drill, washing machine motor. They spark crazy amounts and you'll find metallic residue near the motor.

 

[Tealc]

at the moment the gpu fan is pulling air from outside the box and exausting the hot air into the box.

Are you sure? What card is it?

 

[semajjames]

yes i sure

it did surprise me

the card is a gainward bliss 7800 gs

i can feel it blowing air at my hand when i put it next to the fan inside the box

 

[numatic.nathan]

yes i sure

it did surprise me

the card is a gainward bliss 7800 gs

i can feel it blowing air at my hand when i put it next to the fan inside the box

I'd say from the look of the cooler it has a rear exhaust to blow the air out.

 

[semajjames]

ah wait i just rechecked a little more scientifically with a cigarette paper and in fact the fan is blowing hot air out side the box

 

[Tealc]

Yes well the hand test can often be misleading.

A bit of paper is usually a better guide.

Wasn't able to get a conclusive image of the Bliss 7800 GS as it came up with several different types. Some strange looking fans there though.

Edit: Fag paper, yes that'll do it.