CPU Fan runs at full speed always
We’ve already talked about the first reason. A CPU fan runs at full speed whenever the temperature of CPU increases. The processor generally uses a sensor that controls the fan speed. If the CPU fan runs at full speed all the time, there might be something wrong either with the processor or the sensor (in the fan). It can also be an issue of the heat sink on the processor.
Sensor Problem causes CPU Fan to run full speed always
The most common cause why a CPU fan would run at full speed is that its sensor is not working properly. The solution here is to replace the fan itself. But you need to see that the processor is not always hot. You can use third-party applications for this purpose. I would suggest a hardware monitor from CPUID or XMeters. It will tell you the processor temperature and thus help you decide if the fan is running without a sensor or with one. If you don’t notice any changes in the processor temperature for long, there is something wrong with the fan sensors. In such a case, replacing the fan would help. Read: How to check your PC’s total power consumption.
Certain Apps can increase the CPU temperature
The processor can heat up due to certain applications too. While gaming and streaming videos can heat it a bit, if it is always running at full speed, there is a possibility that there are certain apps on your computer that are putting too much pressure on CPU. To check this, open the Task Manager. Go to the first tab and click on CPU column heading (it says CPU). That will cause the Task Manager to arrange programs and apps in descending order of CPU usage. It means, the apps using the CPU more will be at the top and the ones using it less will be below them. Watch it for a period. It will give you an idea of apps/programs that might be using up CPU causing the CPU fan to run at full speed all the time, always. Based on that, you may try removing the top CPU-consuming apps from the computer and then check again if it helps. If the CPU fan is running at full speed still, check out the heat sink of the processor.
Changing the Heat Sink of processor
If you find that the fan sensor is working and there are no apps using up significant CPU resources for long periods, you may want to replace the heat sink of the processor. Heat sinks absorb extra heat from the processors. They can be replaced easily if you have been playing with the hardware of your computer. For others, the best way is to get a technician to do it as doing it on his own may damage the fan. Make sure the computer is turned off before you remove and re-attach the CPU fan. The heat sink is a coarse alloy (generally Aluminium) attached to the processor with the help of a white substance. If the substance dries up, it too may cause the sink to function properly so you would want to take a look there (if you can open the computer) before changing the heat sink. Read: Video card not detected but the fan is spinning
General tips to avoid computer fan running high speed all the time
Keep the computer clean. You can buy compressed air and use it on the computer motherboard from time to time. Remove, clean, and fix back Random Access Memory sticks (RAM). Always clean the inside of your computer after removing its power sources. That includes batteries if you are using a mobile device. More tips here on how to physically clean up your Windows computer, mouse & keyboard. Let us know if you have any other ideas! Read next: How to fix Overheating and Noisy Laptop Fan issues.
