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Wierd problem with my CPU fan...

By Fyei · 5 replies
Feb 27, 2008
  1. Recently ive been having a number of computer woes, but the latest one involves my CPU fan. Whenever I try to turn on my computer my fan trys to spin up but fails miserably. It tries and tries, but never manages to spin up fast enough to keep turning. This is remedied however if I physically try to spin the fan, then it maintains a steady speed of about 400-650rpm.

    Now this from my eye's point of view looks VERY slow plus there is very little air flow actually coming out of the fan. What should I try to do to fix this? The PC doesnt overheat during general usage but I fear if I try to game on the machine ill break something.

    Ive thought about just buying a new fan but I dont want to do this unless this is all it can be, I dont want to spend £20 on a new fan only to find that it was a faulty connection on the motherboard.

    Cheers for any help.
  2. kimsland

    kimsland Ex-TechSpotter Posts: 14,524

    The CPU fan sucks air in (it is mounted on the Heat Sink)
    Is that the one you are speaking of?
    Or the case fan that blows air in (this depends if you have two case fans 1 In, 1 out)

    Either way, (referring to your motherboard's manual and antistatic precautions, and removal of all power)
    You could blow out all internal dust, reseat the fan plugs (on the motherboard) and it is possible to re-grease your current fan (if you do not wish to purchase one)

    To re-regrease the fan:
    Purchase some grease (actually you just need a finger tip, and it must be high temp - saying sewing machine type grease)
    Remove all power to the computer
    Remove the fan from the computer assembly (ie unplug and unscrew)
    Peel back the label on the fan (usually big round white sticker)
    Remove the small grummot (usually black rubber or plastic cover- and easy to lose)
    using anything small, poke a little grease inside
    Put the grummot back on, and the label
    Refit the fan, and reconnect
    Put all your power back in, and power up.
  3. Fyei

    Fyei TS Rookie Topic Starter

    Its the CPU fan which sucks air away from the CPU. Ill try re-greasing it like you said, cheers.

    If that doesnt work im just going to buy a new fan... this ones getting quite old anyway. Just as a question though, is there any way theres a faulty connection on the motherboard stopping power reaching the fan or something similiar?

    Cheers anyway :)
  4. kimsland

    kimsland Ex-TechSpotter Posts: 14,524

    The CPU fan sucks air in (as ealier stated)

    Yes it can be a faulty connection
    By the way, you are aware that the CPU fan is thermostatically controlled by some boards. Which means it will not turn on for a few seconds on system startup. (until it gets warm) Usually it does give a half turn on system startup though.

    You may need your manufactures motherboard's manual to confirm this.

    Also, yes try reseating the power plug onboard first

    Cheers anyway to you too :)
  5. Fyei

    Fyei TS Rookie Topic Starter

    Ive done a bit more experimentation into the matter, regreasing the fan doesnt work but I think ive found a bit of a pattern in why its screwing up.

    When I first turn the computer on after its been cold for a few hours the fan never starts, I can bring it into windows and all the fan does is try to spin up and fail at life doing so. If I restart however, the computer struggles at first but eventually with my fingers help it can start spinning.

    Its almost as if its lacking the capacitance to run, the first bootup the capacitors arnt charged and it simply cant run the fan whereas on the second bootup it has enough to spin up with a little help and maintain a speed, albeit one ranging from 400-1000rpm which is pretty pants seeing as how my fan is meant to run at 1500 normal.

    Motherboard problem perhaps? Ive never heard of anything like this happening before though...
  6. Tmagic650

    Tmagic650 TS Ambassador Posts: 17,244   +234

    You could try soaking the fan in some WD40 for a while... but it might be better just to replace it
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