Symptoms
- CPU cooler fan doesn't spin when the PC is powered on
- System shuts down shortly after boot, likely from overheating protection
- BIOS may show a CPU fan error or warning at startup
- Fan spins briefly then stops
Likely causes
- CommonFan cable disconnected from the motherboard's CPU fan headerThis is a common and easy-to-fix cause, especially after cleaning or building.
- PossibleFan plugged into the wrong header, which the motherboard doesn't monitor the same waySome boards behave differently for CPU fan vs. case fan headers.
- PossibleFan motor has failedFans do wear out, especially older or lower-quality ones.
- PossibleBIOS fan control setting causing very slow or no rotation at low temperaturesSome 'silent' fan curves keep the fan nearly off until temperatures rise, which can look like it's not working.
What to do
- Power down and unplug the PC before checking anything inside the case.
- Confirm the CPU fan's cable is firmly connected to the motherboard header labeled CPU_FAN.
- Check BIOS for a fan speed reading; if it shows 0 RPM, the board isn't seeing the fan spin at all.
- Try connecting the fan to a different compatible header temporarily to rule out a bad header.
- Check BIOS fan curve settings in case an aggressive silent profile is keeping the fan off during this test.
- If the fan still won't spin on a known-good header and power, replace the CPU cooler or fan.
Tools and parts
- Screwdriver
CPU cooler or fan replacementSearch: “CPU air cooler compatible with your socket”
When to call a pro
If the fan doesn't respond on a known-good header, replace the cooler promptly rather than risk running the CPU without adequate cooling.
Safety
Use caution
Don't let the PC run for more than a minute or two if the CPU fan truly isn't spinning; shut it down immediately to prevent heat damage to the CPU.