CPU Fan Speeds up and Slows Down

[DutchDude]

My computer not works properly when i restart it. I think problem is related with fan on the motherboard. When i restart my pc fan speed increase(really high) but after 20 minute it went really low. Does anyone know why computer fan slows down and speeds up automatically?

[Rawko]

computer fan slows down and speeds up due to overheating and throttling, You can make the fan more quiet by lowering the voltage to 7 or even 5V. I will suggest you not to take replacing decision at an instant try removing wire around fan and just see that you don't have any in wanted material with your fan.

[deoWo]

It is likely its the automatic fan speed is enabled in bios....it speeds up and slows down according to cpu load, however if it makes grinding sounds you need a new one and the simplest implementation to control the temperature of the processor can be constructed using the temperature sensor and the PIIX4E southbridge to throttle the processor.

[Hamir]

Set BIOS settings to run 100% all the time, disabled all power saving options and etc. Even switched the CPU fan to a system fan port so that there was no speed control. The efficiency of some electrical components, such as voltage regulators, decreases with increasing temperature, so the power used may increase with temperature.