Computer Case Fans: Installing, Replacing, Cooling
from the author of
Building A PC For Beginners
  I'm sure you've heard stories about today's hot running CPU's. Perhaps friends have told you horror stories of how their computer overheated. You've probably run your fingers in front of the vents on your PC, and been surprised at how warm the air was.
   Do you wish for the peace of mind another case fan would bring?
   Well, I have good news. Adding a case fan is a simple operation that you can do yourself, and it will only cost five bucks or so. It can be done with the simplest of tools. Only a screwdriver will be required for the job.
   First, look your case over to see if you have an empty fan vent available. Fan vents come in standard sizes. 60mm, 80mm, and 120mm are the most common. Often, the 60mm will be a double vent, utilizing a pair of 60mm fans that can be purchased as a set.
   I have found that 80mm is the most common size for a fan on the back of a case, while 120mm is often found on the case's bottom.
   If you have any doubts about a vent you find, go ahead and take the side off your case and check it out. First, unplug your computer, and disconnect the keyboard, video, printer, and any other cables. Then, remove the side by taking out the two or three screws that hold it at the panel's back edge. The panel will then slide back.
   Some computers may not have an extra vent. Since sheet metal work is outside the scope of this article, if this is so, I advise you to go no further. However, if you do have a vent available, the next step is to check out your power connectors.
   Fans can plug in at two places. To the power supply, or to the motherboard. Since the port on the motherboard may be difficult to locate, I recommend using one of the standard 4 pin connectors coming from the power supply.
   The odds are you will have two or three of these going unused in your computer. They are the same type of connector that provides power to your hard drive and CD/DVD. If you have one available, and an open vent, then you can mount another case fan.
   There is one more thing to do before going shopping. Measure the size of the vent just to make sure it's the size you think it is. Guesswork could mean an extra trip to the store. Save yourself some time and use a ruler.
   Let's say you can use an 80mm fan. At the store, you'll be looking for one of that size, that has a 3 to 4 pin adaptor included, since we are going to use the 4 pin connector from the power supply. Adaptors can be purchased extra, but this is bad economy, as many manufacturers include them as a matter of course.
   Generally speaking, the fan will be rated at 12 volts, with an input power of 1.8 watts. About $5 or $6 dollars will get you a constant speed fan running at 2500 RPM.
   When you take the fan out of its box, the first question that comes to mind will probably be "Which side is the front, and which is the back?' On many fans, the front and the back look exactly the same. Even the screws that hold it in place can be run in from either side. So how can you know which way to turn it?
   Here is a clue: most manufacturers put their company logo on the side that will be exposed inside the case. The side with the UL label goes against the grill itself. Mounted this way, you will have an exhaust fan. If you want it to draw fresh air  from the outside, just flip it over.
   If questions still linger in your mind, install the fan using only 2 screws to hold it in place. If air is going the wrong way, it will be easier to take out 2 screws than all 4.
   Don't try hooking it up outside the case. You can nick your fingers in the blades, and damage the fan.
   The fan is mounted by running the screws in from the outside of the case (in most models). This way, if a screw comes loose, it doesn't go pinballing down through the components, lodging somewhere that could cause a short circuit.
   Take care in tightening the screws. The plastic threads in the fan's body can be stripped easily. Snug them down "finger tight", but nothing more than that.
   Now, take the 3 to 4 pin adapter and connect it to the fan. These plugs are keyed to fit together only one way, so there should be no problem getting it right. If you are still concerned, remember that the black wire is the ground, and the red is the "hot" wire. So just check to see that black connects to black, and red to red.
   At the other end of the adapter will be a 4 pin plug. This connects to the 4 pin, 4 wire lead coming from your power supply. It too will only connect together one way. With this plugged in, you are ready to test the fan.
   Connect the power card, monitor, keyboard, mouse, everything as if you were getting ready for regular use. But leave the side panel off. You'll want to observe the fan.
   Turn the computer on and watch. The fan should start immediately. Check to see if the air is blowing in the right direction.
   If all is right, turn the computer off, and put the side panel back in place.
   Congratulations! You've installed a case fan.
Installing the CPU
Parts of the Motherboard
Computer Definitions
Selecting Parts
Computer Power Supply How much is enough?
Table of Contents
Install AGP card
Install RAM
Computer Cooling Problems