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    CPU fan either at full speed or off issue

    Discussion in 'Hardware Components and Aftermarket Upgrades' started by Willmo, Mar 17, 2016.

  1. Willmo

    Willmo Newbie

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    After swapping my fan and heatsink on my Acer Aspire 7740G it now either runs at full speed or not on at all. Temps are all good, i have tried an old bios, the latest from Acer and a modded bios and still no change. The fan is the same make and model as the last one and non removable/swappable

    It happens in bios as well as windows so im pretty sure its a bios, motherboard or fan issue. Anyone have any ideas or suggestions of what to try?

    Thanks in advance

    Will
     
    Willmo, Mar 17, 2016
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  2. Willmo

    Willmo Newbie

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    Just tried the old fan plugged in with the new heatsink and the fan spins correctly (regulates speed by temperature). I can see a way to replace the fan on further inspection so i have ordered a new one. I will post the results back here to help others with the same issue
     
    Willmo, Mar 17, 2016
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  3. John Ratsey

    John Ratsey Moderately inquisitive Super Moderator

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    The fan connecting cable usually has 3 wires. One of these is for a speed sensor so the BIOS knows what speed the fan is running at. If that data isn't getting through then, if the temperature requires the fan to be on, it will be run at full speed.

    John
     
    John Ratsey, Mar 18, 2016
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  4. Willmo

    Willmo Newbie

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    Thanks for your reply John, yeah its a PWM (4 Pin). Agreed, i thought this is the issue but as far as i can see the cable is intact so it must be at the motor end
     
    Willmo, Mar 18, 2016
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