Case fan mod.

[DezGalbie]

Does anyone know what would happen if I was to mod a 12V case fan to be powered by USB?

From what I understand, USB supplies 5V. So would the fan still work, but at a lower RPM? And if this is the case, will it still be any use for cooling?

The PC in my office is having some issues and needs some extra cooling on the graphics card. Wiring up a case fan in this manner is the only way I can think of to fix the problem without having to buy any parts which I don't already have lying about. It's an old pre-built system with a GeForce 405 graphics card. The little fan on the card has died and so it has passive cooling from the heatsink only. This causes the card to overheat and the system to crash. Due to the annoying OEM designed case there's no space within the case to place a fan pointed at the card. But there is some mesh on the case allowing airflow from the outside. So my plan is to attach the fan to the outside of the case blowing air inside through the mesh and towards the graphics card (and power it via the front panel USB).

Anyone have any thoughts on this?

[BobVonBob]

I'd be incredibly surprised if a case fan managed to spin at all on 5v, and if it did it wouldn't push much air. There are a few options, you could get a USB fan, you could get a USB to 12v step up converter, although that has the possibility of drawing too much current and breaking something (not likely, but possible, especially if something stalls the fan), or you could put a small hole in the case and use any spare power connectors and a *insert power connector* to fan header cable.

 

It is also worth noting that you probably won't get much airflow out of a fan pointing in the side of a case, and it might not send air in the right direction to cool well, but the 405 isn't a super high heat card to begin with, and at the very least it can't hurt.

[Guest]

Quote

So would the fan still work, but at a lower RPM?

That depends on the starting voltage of your fan of choice. If it's anything over 5V, your fan won't start. If it's less than 5V, it will start and will work in the lowest RPM range. Obviously, regardless of whether it's a PWM or voltage-regulated fan, you won't have any regulation at all.

 

If you go with a step-up converter, you might be able to run a 12V case fan, but you'd run into risk of drawing more current than recommended and frying something.

 

Other than that - it's an office PC. I'd rather pester whomever is responsible for equipment to replace or fix it, rather than jury-rig some solution myself, lest your solution blows something up.

 

[Bananasplit_00]

5V isn't going to be pushing much air, the fan might spin, but 7V is the lowest I have gone