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power supplyIn my many years of IT and Help Desk work, and being the resident geek for everyone, I have had many a relative or friend ask me what to do about a Windows-based computer (not sure if Macs do the same thing) that turns on and acts just fine and then inexplicably shuts off minutes later, for no apparent reason. It is a common problem for many PC desktop users, incredibly aggravating, and more common than you might think.

The problem is that this seems so sinister. You saunter over to your desk, flip on your PC, and everything looks peachy when it starts up. Then a few minutes later, in the middle of watching yet another YouTube video on who knows what, you PC decides to take the law into it's own hands and shut-down with no notice, no warning, and you don't have a choice.

Why, for the love of Steve Ballmer, why? Well, since I have had a long history with many a PC, let me explain the scenario I have seen most often. When the PC shuts down abruptly like that, it is doing it for your own good. No, seriously, please believe me, put down the sledge-hammer, don't even think about doing your own DIY PC demolition just yet.

The PC has a built-in safety mechanism that turns off the PC if the power-supply gets overheated. The power-supply is that big portion of the PC case that generates and coverts voltages for you and has the power cord plugged into it. You'll notice that in general, the PC will have a giant fan on the backside of your system right near the power cord socket. This is power-supply fan. When this fan stops working, the power supply overheats and shuts your computer down. Here is what to do about it.

Power supply hack(click thumbnails to view gallery)

While this safety mechanism prevents fires in many cases, it is also extremely annoying, after you've typed the same 12 lines into a document, and wondering whether your computer simply doesn't like the word "contusion." To test this theory, try a little experiment. Grab a fan from somewhere in your house, and plug it in near your computer. Take off the computer's side panel and point the fan right at it. Use caution here, and don't let little ones put their hands into the open-PC case. I also don't recommend running your PC like this, we are only troubleshooting here, but be careful.

If the computer stays on for long periods of time with the fan continually running, you know that this was in fact the issue. In most cases that fan inside the power supply is the culprit.

Some newer PC's you will not be able to do this, since the fans are much smaller, but for most PC's that are still a full sized tower, it works just fine.

A new fan that should cost $15 or so at RadioShack

A few screwdrivers (flat-headed and Phillips)
A workspace that will allow you to clean out the power supply without getting dust everywhere

Less than an hour
  1. Since you already have the cover off the side, turn off and unplug the PC, then remove the power supply. Usually there are a few screws in the rear of the PC that hold the power supply in place. Usually you won't have to remove all the drives to get it out, unless you have a really cramped case.
  2. Next remove the cover from the power supply and unscrew the fan from the metal casing. Oh, yeah, disconnect the cable first, it helps the whole not-getting-electrocuted thing. If needed, unplug all the leads from your hard drive, optical drives, and other components. WRITE DOWN which number goes to which component (P4 to Hard Drive) or you will get them connected again, and they have to go to the same connections. Clip the red and black wires, but leave enough wire to work with later (4″ at least). This picture shows the fan already removed, and the two wires clipped at the far right center.
  3. Go to RadioShack or other friendly computer or electronic parts store and buy a fan of the same rating and voltage to replace the one that is Ka-Put! This will usually run you about $15 bucks. Not bad considering a new power supply will run you $50-$100 at least. This picture is of the old and new fans.
  4. Solder the wires of the new fan to the leads from the old fan, black to black (or blue), red to red.
  5. After soldering the wires together, put the fan back in place and screw it into the metal casing.
  6. Next put all the power supply back together. Some have plastic shielding you have to put back in, some snap-lock over the circuit board, so be sure to look at it closely and get everything back together, or you can have problems.
  7. It's actually a good idea to test out your newly hacked power supply before you put back in again, just be sure it is grounded, by touching the metal casing to the PC's frame you should be good.
  8. Viola! Eureka! Osama! It works. Sweet. Anyway, have fun with it, see if you can hack it. It is pretty simple, and saves you a bunch of cash. It takes about an hour or so, and that includes the trip to a nearby RadioShack. Cheers! Happy computing!
NOTE: It is a good idea to know a little bit about computers and their wiring before attempting something like this, and if you don't know what you are doing, please ask a friend for help. No use destroying your PC or yourself (much harder to replace you) in the process over saving a few dollars. If you try this out, you do so at your own risk. This is only what worked for me in this situation.

  • Juan

    Why don't you just get a new power supply?
    Might cost $5-$10 more but quicker and less hassle.


  • Peter

    You imply it but don't explicitly mention that you should power up the machine and actually look at the power supply fan to be sure it is not spinning. I've had the processor fan fail and it produces the same overheating symptoms. You want to be sure you are replacing the bad part. Sometimes you can also spray a little WD-40 on the fan bearings and get it spinning again. I've had that fix work for years.

    Juan - If you can get a power supply for $10 more than a fan, you are either buying a very cheap (as in crappy) power supply or a very expensive fan.

  • 2 Comments / 1 Pages

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