When the CPU fan doesn't rotate, it can be a serious issue as it can lead to overheating of the CPU, which may cause system instability, performance degradation, or even permanent damage to the CPU. Here are some steps to troubleshoot and fix the problem.

Check the Power Connection

First, ensure that the CPU fan is properly connected to the motherboard. The fan usually has a 3 pin or 4 pin connector that plugs into the CPU fan header on the motherboard. Disconnect and reconnect the fan connector firmly to make sure it is seated correctly. Sometimes, the connector may become loose during computer assembly or while moving the computer. If the fan still doesn't rotate, check the power supply unit (PSU). Make sure the PSU is functioning properly and providing power to the motherboard. You can use a PSU tester or check the power cables connected to the motherboard. If the PSU is faulty, it may not be supplying enough power to the CPU fan.

Inspect the Fan Blades and Motor

Visually examine the fan blades for any signs of obstruction. There could be dust, debris, or even a foreign object stuck between the blades, preventing them from rotating. Gently clean the fan blades with a soft brush or compressed air to remove any dirt or debris. If the blades are free moving but the fan still doesn't rotate, the problem may lie with the fan motor. Some fans have a built in LED that lights up when the fan is receiving power. If the LED is not on, it may indicate a motor failure. In this case, you may need to replace the fan.

BIOS Settings

Enter the BIOS (Basic Input/Output System) of your computer. This is usually done by pressing a specific key during the computer's startup process, such as Del, F2, or F5, depending on your motherboard. In the BIOS, look for the fan speed control settings. Make sure the fan control mode is set to the appropriate option. Some motherboards have a "silent mode" or "auto mode" that may adjust the fan speed based on the CPU temperature. If the fan speed is set too low or disabled in the BIOS, it may not rotate. Set the fan control mode to "normal" or a mode that allows the fan to operate based on the CPU temperature.

Software and Drivers

Sometimes, software issues can cause problems with the CPU fan. Make sure your computer's operating system and motherboard drivers are up to date. Outdated drivers may not communicate properly with the motherboard's fan control circuitry. You can visit the motherboard manufacturer's website to download and install the latest drivers. Additionally, some monitoring software may interfere with the fan's operation. Try uninstalling any third party fan monitoring or overclocking software that you have installed and see if the fan starts working again.

a non rotating CPU fan can be fixed by checking the power connection, inspecting the fan hardware, adjusting BIOS settings, and ensuring proper software and driver functionality.