# fan not working (sometimes)



## Noster (Oct 28, 2011)

like many laptop owners i have overheating issues. the original fan from my hp pavilion dv5 has broken down completely, so i replaced it about a month ago. 
the new one was working reasonably good until recently ive noticed it doesnt start with windows everytime. when that happens the laptop starts overheating. im monitoring the temperature so i shut it down before it crashes. then when i boot it again the fan works (most of the time). sometimes i have to reboot it again to start the fan. 
any ideas what might the problem be and how to fix it?

ive also tried a few bios programs to adjust the fan speed but neither could load/identify my bios


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## cl0udedth0ught (Sep 29, 2004)

First off, not all fans are adjustable and not all fan monitoring tools are reliable. Have you went into your BIOS (before the OS loads) and checked the temps in there? Are you playing games or doing something intensive when it shuts down?


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## Done_Fishin (Oct 10, 2006)

Some laptops, and by some I mean I see quite a few, only set the fan working when the cpu temp gets high .. it's part of the design called ACPI 

What is ACPI? - A Word Definition From the Webopedia Computer Dictionary



> Short for Advanced Configuration and Power Interface, a power management specification developed by Intel, Microsoft, and Toshiba. ACPI, which will be part of the next version of Windows, enables the operating system to control the amount of power given to each device attached to the computer. With ACPI, the operating system can turn off peripheral devices, such as a CD-ROM players, when they're not in use. As another example, ACPI will enable manufacturers to produce computers that automatically power up as soon as you touch the keyboard.



Sometimes a laptop BIOS isn't recognised as having or being fully complant with this feature when installing windows. This results in a laptop that might overheat and shuts down. If this happens one should hit F7 during installation (when prompted to hit F6 for other drivers) to disable ACPI and install APM (automatic power management)


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## Noster (Oct 28, 2011)

cl0udedth0ught said:


> First off, not all fans are adjustable


how do i know if the fan in my lapton is adjustable or not?



cl0udedth0ught said:


> not all fan monitoring tools are reliable.


ive tried several temperature monitoring tools simultaneously, they were all giving identical result. besides, as the temperatures given by the tools increase, the performance gets a lot worse and if i dont close any applications and give more space for the laptop to breathe it overheats and shuts down. the temperature readers must be about right



cl0udedth0ught said:


> Are you playing games or doing something intensive when it shuts down?


i dont really play games but it seems running more applications at once (giving the cpu something to think about) increases the temperature. but really its more to do with whether the fan is open or blocked (ie how the laptop is placed on table etc.) given the fan is running at all



> Some laptops, and by some I mean I see quite a few, only set the fan working when the cpu temp gets high .. it's part of the design called ACPI


i doubt my laptop is using ACPI because normally the fan starts as soon as the pc is turned on except the times when the fan does not start at all, resulting in the laptop overheating. anyhow, is there a way to find out whether the laptop has ACPI implemented?

two questions remain unanswered:
1 how do i ensure the fan starts every time the windows starts?
2 how do i increase fan speed?


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## Done_Fishin (Oct 10, 2006)

I'd start first, if you haven't done so already, by blowing some air through the fan to ensure that no dust or anything is sitting inside blocking it and stopping it from starting up. 

fans are usually (in PC's) driven from a 12Volt source and a transistor that varies the voltage given to the fan motor. The PC checks the CPU temperature and decides whether it requires to drive the fan harder in order to drop the temperature. The voltage for a 12Volt fan must be in excess of about 6 volts since there is a minimum voltage required to allow the motor to spin. The CPU just varies the voltage drop across the transistor (a very simple explanation of what actually happens) in order to vary the motor speed.
A laptop fan though usually runs on 5Volts. It is usually either set to run or not run .. depending upon CPU temperature. Because it is a laptop fan, the design has taken into account that running the fan when not on mains power might discharge the battery too quickly, so the fan is usually set to run "when required". On the many occasions that I have serviced laptops I have found very little of help in the BIOS to allow me to tweak any settings .. the only one I have seen on occasions is to set the fan to run all the time when on mains power. However not all laptop bios's are the same and too many do not give any options.

Apart from blowing out the fan & vents with some compressed air, it is a good idea to ensure that the laptop always has good breathing space underneath. I am not saying that you fall into this category but far too many laptop owners do not understand that the laptop should NOT be used on beds, pillows, cushions , carpets, thick tablecloths etc .. since the fan sucks in dust, hairs and other debris which eventually cause clogging and blocked ducts/vents. should always be used on hard surfaces with little or no fabric below and certainly not allow anything to come in close proximity of the vents that allow the fan to suck in air.

One other item that might be playing a part of your heating problem is Thermal Paste on the CPU heatsink. This may require replacing after thoroughly cleaning off any old paste from both the CPU & Heatsink surfaces where the two mate.


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## cl0udedth0ught (Sep 29, 2004)

^ditto what done_fishin said


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## Noster (Oct 28, 2011)

Done_Fishin said:


> I'd start first, if you haven't done so already, by blowing some air through the fan to ensure that no dust or anything is sitting inside blocking it and stopping it from starting up.
> 
> fans are usually (in PC's) driven from a 12Volt source and a transistor that varies the voltage given to the fan motor. The PC checks the CPU temperature and decides whether it requires to drive the fan harder in order to drop the temperature. The voltage for a 12Volt fan must be in excess of about 6 volts since there is a minimum voltage required to allow the motor to spin. The CPU just varies the voltage drop across the transistor (a very simple explanation of what actually happens) in order to vary the motor speed.
> A laptop fan though usually runs on 5Volts. It is usually either set to run or not run .. depending upon CPU temperature. Because it is a laptop fan, the design has taken into account that running the fan when not on mains power might discharge the battery too quickly, so the fan is usually set to run "when required". On the many occasions that I have serviced laptops I have found very little of help in the BIOS to allow me to tweak any settings .. the only one I have seen on occasions is to set the fan to run all the time when on mains power. However not all laptop bios's are the same and too many do not give any options.
> ...


thanks for the thorough yet understandable answer 

yes the laptop has been cleaned for dust, the fan was replaced just two months ago.

no i dont use the laptop holding it on pillows, carpets etc i realised it needs some breathing space a long time ago 

is it complicated to make the fan run all the time regardless of cpu temperature?

Thermal Compound Grease Paste CPU Heatsink RROD | eBay is this the kind of thermal paste u were talking about?


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## Done_Fishin (Oct 10, 2006)

arctic silver is far better .. 

Arctic Silver 5 Thermal Compound Paste (3.5g) | eBay

they say for one cpu but you only need a small spot that when compressed flattens out to cover JUST the cpu heatsink area . literally small garden pea amount or less.

you'd have to make a hardware mod to your laptop fan to give it 5 Volts permanently and after that there is no guarantee that it would last very long .. my experience of fans is that they last longer when run at slower speeds .. bearings/sleeve gets hot, grease or oil dries creating resistance and causes more heating problems until it seizes. Everything is possible if you understand electronic circuitry .. but also every modification usually requires further modifications (as denoted by Murphy's Law .. and he is always RIGHT!) :smile:


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