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Power supply fan

Posted on 2001-08-25
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Last Modified: 2013-11-10
Should the fan that is connected to the power supply be spinning constantly or only when needed? If I have determined that the fan NEVER spins during the course of having the PC running for 2 hours, should I replace the power supply?
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Question by:rsorrent
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by:oldgreyguy
ID: 6424799
depending on the cost/quality/design of the power supply, the fan can run in one of several modes:

fan always on, constant speed
fan speed fluctuates according to temperature sensors

fan never works........ broke or your system is running real darn cool

If the fan doesn't spin on start up, I would be suspect....... take a punji stick (ok, so most folks call them bamboo skewers), and try to turn the fan blade...... if it resissts at all, then I would replace the power supply

bill
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by:genguy
ID: 6424847
If the fan never runs, then it's likely that the fan itself has failed. Just the fan can be replaced quite easily. If this is an older pc power supply you may want to just replace the whole thing, since you'll get a higher wattage unit that would support future system upgrades. If it's a server or something else with a more expensive power supply, the best route would be to just change the fan.
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by:jhance
ID: 6424934
In virtually all PC power supplies, the internal fan is a 12V fan and it is driven off of the 12V supply line in the PS.  A mechanical failure in these fans is not at all unusual and in many systems this presents no real problem.

Unless you are having an overheating problem, I'd say leave it alone.  If you are having a problem, or it just bothers you, either replace the entire PS or if you are moderately experienced with electronics repair, replace or repaid the fan yourself.  BE WARNED HOWEVER!!  If you don't know what you are doing you can create a significant danger to yourself and others if you make a mistake here. So you be the judge of whether or not you can do this.

The fans themselves are simple enough to replace but you need to find one that is the same size.  Radio Shack and other electronic stores often have these but take the old one for a match.

I've had good luck with repairing these fans.  The usual problem is a lack of lubrication in the bearing which is a crude thing to begin with.  Usually you can just peel back the stick-on label and get access to the fan shaft and bearing.  I've found that ONE DROP (no more!!) of light machine oil will fix these things for the life of the machine.  Put the oil in the small pocket where the bearing is and stick the label back down.  Let it soak in for a few minutes and then test the spinning by hand.  You should feel it spin smoothly.

There is really nothing else to go wrong with such a fan.  The fan blade/shaft is the only moving part.  The other part is a coil and I've never seen one go bad.

If you don't have a clue about all this, just buy a new power supply.  They are pretty cheap..
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by:pbessman
ID: 6425006
Most power supplies are sealed and sealed for a reason.  If this is a new system, TAKE IT BACK TO THE PLACE YOU BOUGHT IT!  I have never seen a power supply fan which does not spin up when power is applied.  Other fans in the system, yes they do have temp controls for them.  If you NEVER hear the fan the power supply should be replaced before it potentially damages your system.
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by:pbessman
ID: 6425011
Some power suplies have fans which can be replaced fairly easily.  It is the risk of bumping one of the wires inside that makes this a potentially DANGEROUS situation.  Some of these components store a tremendous amount of energy.  You could be seriously injured or worse.  If you must BE CAREFUL.  It is much safer to replace the unit as a whole.
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by:jhance
ID: 6425055
>>I have never seen a power supply fan which does not spin up when power is applied.

??? Where have you been living.  I've seen so many siezed up fans I've lost count.  In my experience it's the #1 PC repair problem.

>>Most power supplies are sealed and sealed for a reason

In fact, most are not "sealed".  Unless you call 2-4 small phillips screws sealed.  By your definition most PC cases are sealed as well.

>>Some of these components store a tremendous amount of energy

True but not in a way that is very dangerous.  Virtually all PC power supplies are switching types and the energy storage device in them is an inductor.  The nice thing about inductors is that they don't store energy for more than a few mS after the input power is removed.  A PC power supply is completely safe to disassemble once the AC input power is removed.  My concern was with improper re-assembly and having a hot wire short to the case or something similar.
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by:HDWILKINS
ID: 6425083
The fan on the power supply MUST always be rinning.

If it is not, heat builds up in the power supply which causes resistance.  Resistance lowers voltage and low voltage can confuse or kill a machine.

Buy a new power supply.

HW
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by:genguy
ID: 6425110
The only seal is a sticker that says void if removed, it's for warranty purposes. If it's a few years old then the warranty has expired anyway. As far as safety goes, remove the plug from the wall.
Changing a fan is well within the grasp of a novice, but if you don't feel comfortable, or aren't really interested, then get it done by a repair shop.
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by:pbessman
ID: 6425273
JHANCE it says,"I have never seen a power supply fan which does not spin up when power is applied.
 Other fans in the system, yes they do have temp controls for them.  If you NEVER hear the fan the power
supply should be replaced before it potentially damages your system."

DUH! it is a problem, it's broken, it is not working as it is supposed to.  Someone else said,"depending on the cost/quality/design of the power supply, the fan can run in one of several modes:fan always on, constant speed
fan speed fluctuates according to temperature sensors."
<I WAS SAYING I HAVE NEVER SEEN THIS>

READ MY STATEMENTS before you JUDGE them.
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by:pbessman
ID: 6425285
"The only seal is a sticker that says void if removed, it's for warranty purposes."  NOT SO, many are riveted together making a drill and a rivet tool an added expense.  Cheaper and easier to replace unit as a whole.

"Changing a fan is well within the grasp of a novice, but if you don't feel comfortable, or aren't really
interested, then get it done by a repair shop."  Every manual I have used for instructing my A+ classes advises against opening monitors and opening Power Supplies.  Their cost is not worth trying to repair components.  If it is a NEW system you should take it back without delay.  Never FIX anything that should be REPLACED under WARRANTY.
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by:fmkjr
ID: 6425294
Dont mess with the power supply, if you happen to slip with the screw driver and bend or break a connection you could start a FIRE when you reapply power, also you could give you self a REALLY BIG shock if you happen to short one of the caps (it wont kill you but will scare the hell out of you, spark, and maybe hurt you)
With these two things in mind and the fact that a power supply is less then 25 bucks why screw with it.

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by:genguy
ID: 6425317
>>Never FIX anything that should be REPLACED under WARRANTY
Quite correct.
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by:d_hall
ID: 6425701
rsorrent -  How about giving us the make and model of the PSU so we can verify whether it has speed control or not?  Some do, and it may be that it has a good heatsink and/or you have really good case airflow, so the fan doesn't need to come on.
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by:Roscoe
ID: 6426696
rsorrent - all of these answers are excellent - am not looking for points, but want to summarize to help you decide... lots to consider.

1) Should fan be running? Yes, for  most part - most consumer clone power supplies (p/s) have a fixed speed 12V fan. I agree that even the thermostatically controlled fans normally turn on for a few seconds on startup, if only as a self-test....  I've had to replace too many components over the years whose useful life was shortened due to heat damage - which, like damge due to electrical surges, is invisible.... Noise aside, there's no such thing as too much airflow....
2) When should you replace? If you're on warranty, no brainer. If uncomfortable with poking around electrical stuff, ditto. If p/s is sealed with rivets etc, ditto. If you've had the unit for a number of years, odds are (unless you're a member of the UPS religion like I am) that it has taken a number of "hits" with power surges, etc. affecting reliability, ditto. If you're on a customer site, the cost of the UPS is much less than the billable rate being charged for your labor... ditto. Standard cautions apply, as well as the obvious - make sure everything gets plugged back in properly!
3) When should you repair? If the fan blades appear to be stiff or hard to turn (note: test rotation with POWER OFF), then the odds are it's lubrication. Hard to believe that your system runs cool enough not to eventually cause a thermostat to kick in. If you're broke and/or have time and/or are handy and/or careful and/or system appears to have nothing else wrong with it, the lubrication and disassembly tips given are valid.

Above all else: Remember, safety first....
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pbessman earned 150 total points
ID: 6426901
To quote:  http://howstuffworks.lycos.com/power-supply4.htm

"Power Supply Problems
The PC power supply is probably the most failure-prone item in a personal computer. It heats and cools each time it is used and receives the first in-rush of AC current when the PC is switched on. Typically, a stalled cooling fan is a predictor of a power supply failure due to subsequent overheated components. All devices in a PC receive their DC power via the power supply.
A typical failure of a PC power supply is often noticed as a burning smell just before the computer shuts down. Another problem could be the failure of the vital cooling fan, which allows components in the power supply to overheat. Failure symptoms include random rebooting or failure in Windows for no apparent reason.

For any problems you suspect to be the fault of the power supply, use the documentation that came with your computer. If you have ever removed the case from your personal computer to add an adapter card or memory, you can change a power supply. Make sure you remove the power cord first, since voltages are present even though your computer is off."
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by:pbessman
ID: 6426902
"Make sure you remove the power cord first, since voltages
are present even though your computer is off."
This is especially true in the newer power supplies that support the "standby" mode.
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by:pbessman
ID: 6426920
To Quote another site:  http://www.pcnineoneone.com/howto/powersupply1.html

"Warning: Don't try to replace the power supply fan yourself unless you know what you're doing! It requires some soldering and should only be done by somebody who is familiar and comfortable with such a procedure. I rather recommend replacing the whole unit with a better quality one.

When the actual power supply fails, it can exhibit a number of symptoms. You could experience crashes, data corruption, or hardware failure. Another thing that could happen is that when you turn on your PC, the lights and fans come on, but it doesn't boot, because the BIOS cannot verify a sufficient and consistent power flow is established before it continues the Power On Self Test (POST) and the boot process. Or the PC does not boot at all if the power supply is completely dead and nothing happens at all when you push the power button."

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by:Roscoe
ID: 6427479
I heartily agree with the sentiments expressed and/or quoted by pbessman - the other point I meant to really reinforce is that YOUR comfort level has to match the job at hand. The best customers I've had are the ones who matched their skill and comfort level with the required task, and knew when (or not...) to call for help... the point about ATX power supplies (especially those without a separate on/off isolating switch next to where you connect A.C. input power) is especially valid..... I confess to a blind spot sometimes, as I'm a licensed electrician with high voltage and low level electronics training and experience... as ever, your safety is No. 1, folowed very closely by the trade-offs between replacement cost vs time spent....
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Author Comment

by:rsorrent
ID: 6428606
So many suggestions I will need to carefully review before awarding points. Please be patient for a day or two.

Thanks to all!
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by:pbessman
ID: 6429308
I think there is another electrician here as well.  I am not one, but I know someone who has responded here made a comment the other day that he, too was an electrician by trade.
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Author Comment

by:rsorrent
ID: 6454319
Increased points for two reasons: 1) my delay in grading the response and; 2)the flak pbessman received from other experts
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by:pbessman
ID: 6454403
Thanks.  I am glad you made it through ok.  What was your solution?  Did you replace the unit or just the fan?
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Author Comment

by:rsorrent
ID: 6454413
Ordered the replacement PS; still waiting for delivery but expect this to resolve the issue.
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Author Comment

by:rsorrent
ID: 6481288
Issue resolved; thanks
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