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I have recently pulled the battery out of the motherboard on an old Acer desktop to reset the bios, but when I put the battery back in after about 3-4 hours, and start it up, the cpu fan just keeps getting faster and faster, like it won't stop at all.

Does anyone know of a way to fix this problem?


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Like Darth Android said, check the BIOS. There might be fan speed settings. I would also recommend installing a program to check the CPU temperature or you might be able to check the CPU temp in the BIOS. Sometimes temperature gauges break and report outlandish numbers. If this is the case, you can try to manually set the fan speed using "speedFan". You'd have to make the program start up with windows for the changes to stay on reboot. This program can also tell you the temperature readings for most hardware.

Edit: Also make sure the heatsink is on tight... the CPU might actually be overheating.

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Double check that the fan is set to auto speed in the BIOS, or speed based on temperature. It might reset to always-on as a failsafe when it goes to factory settings.

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In addition to checking the BIOS for an option like "Fan Control", "Fan Speed" or "Thermal Management" you should verify (also in the BIOS) that the frequency scaling for the CPU isn't disabled. For Intel it's called SpeedStep, for AMD it's Cool&Quiet/PowerNow

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up vote 0 down vote accepted

I figured it out eventually by trial and error with the BIOS. Each time I would turn it on, I had about 20 seconds to view something in the BIOS before I would have to power it off from the powerpoint/wall outlet. (I thought it might be too dodgy to run a CPU fan much over 6500RPM)

The BIOS setup software was 'Phoenix AwardBIOS' pictured here:

enter image description here

Once I had booted into the 'BIOS Setup' (Delete key on startup), I quickly moved across to the 'Load Optimized Defaults' from the main menu, and said 'Y' to the confirmation dialog box to load the settings. After that, I quickly pressed 'F10' to save settings and quit.

None of this was complex at all - the issue was that the fan was getting really fast, even by the time I had got into the 'BIOS Setup' from a cold start. It was more about risk management (and knowing that I had enough time to change the settings) without something going "bang" (because it ends up sounding closer to a jet after about 25 seconds). You have to be quick, and you probably need to mentally think through the key strokes before you go in to change the settings!

Once I had saved the settings and quit, the PC rebooted itself, and the fan dropped back down to normal speed.

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