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How to turn a PC fan into an exhaust or intake fan?

Smokin Moose

Fallen Cannabis Warrior
Just for fun, I wanted to show how easy it is to turn a PC fan into an intake, or into an exhaust fan. The fan I am using is quite small, but the objective is still the same. The first step is to find or buy a 12v DC plug adapter. This fan here is rated at 80cfm, which will work for a small box set-up.

Here's is some info on the 12v DC adapter: (Model 420A4141)

Output (DC) 12.0V @ 500mA
Output Voltage VDC(1)
Input 108VAC
Output Volts @ 100% Load 10.20
Input 132VAC
Output Volts @ 100% Load 13.60
Input 132VAC
Output Volts @ 10% Load 17.40
UL(2) UL*
CSA(3) L
Plug(4) 1

Simply cut the wires at the end, and strip down about a ¼ inch of bare wire is showing.

If you don't know which wire to wire up, for instance they're all black wires, don't worry, it will only work one way, and if wired wrong, will simply not work at all. But the idea is, black to black, red to red. This one here that I used, had one black and one red coming from the fan, and from the adapter, one black and one black and white. The black and white wire from the adapter got wired to the all black wire from the fan. And the all black wire from the adapter, gets wired to the all red wire from the fan.

To add another fan, just connect the wires of the same together. All black goes with black, all red goes with red. So you would still only use 2 connectors all together. Here's a few more pictures. But for the most part, I just wanted to show how simple it is. Make sure you get an adapter which is rated DC for the output.

Also a worthwhile consideration is places like radio shack and grainger also have nice 4" muffin fans that move as much as 200 cfm and more, which run on 110 vac. They come with a handy power cord that has a special connector on one end for the fan and a plug on the other end for plugging into the wall socket or humistat / thermostat.


New Member
this is how to wire pc fans to run without the computer. Does not describe how to turn it into a inlet or outlet fan.


New Member
Simply turn them in a different direction. A PC Fan only spins one way, so flip the fan. If the fan spins to the left it is generally pushing air out that way. Just feel for the breeze. Where the Breeze goes, Air goes.


New Member
im looking to put in a 100cfm pc fan in my 1.75x3.5x6 grow box...will a pc fan work just as good as other fans sold on hydro sites?


New Member
Agreed KingJohnC, I like to hear more info on this. I'll start searching :) :Namaste:

I don't have pics at the moment, but my room uses PC fans exclusively. Here is what I have learned:

  1. Run identical fans if using more than one.
  2. Run all fans at the same time. Leaving one fan off will cause a vacuum condition and negate airflow
  3. PC fans can offer near-silent airflow compared to HVAC / bathroom fan options
  4. 12v adapters can be found at most goodwill stores for a buck or two. Load up when you see them

I run these fans: Rosewill RFX-120 120mm Case Fan - Newegg.com

A good way to go is to build a right-angle collector into your nominal duct radius. Something like this:

Create a template with really rigid cardboard or plywood. I paint it black with stove paint to resist moisture as well as abate reflections. These fans are good for 80cfm each, and I can fit three in this setup. It seems to offer sufficient coverage for my small room, and it runs really quiet.

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