CPU Fan Error on Boot – Fix It Now 2025!

A CPU Fan Error on Boot means the motherboard cannot detect the CPU fan’s speed or movement, risking overheating. To fix it, reconnect the fan to the CPU_FAN header, clean the dust, and adjust or disable the Fan Speed Low Limit in BIOS to restore normal cooling.

In this guide, you will learn every trusted and safe way to fix this startup fan error, including expert methods technicians use to find, fix, and prevent it from returning.

What Does the CPU Fan Error on Boot Mean?

A CPU Fan Error on Boot occurs when your motherboard cannot detect the CPU fan spinning or reading its speed. This is an automatic CPU safety system designed to prevent the processor from getting too hot or crashing.

In simple terms, the error warns you that the processor may not have proper cooling. The fan is unplugged, spinning too slowly, or misread by the BIOS. Fixing it ensures your CPU runs safely, and your PC starts correctly.

Common CPU Fan Error Messages Explained:

Most motherboards display different versions of the same warning. Here are the most common ones you might see during startup:

• CPU Fan Error: General message meaning the fan is not detected or spinning.
  
• CPU Fan Speed Error Detected: BIOS can not read a proper RPM signal.
  
• CPU Fan Not Detected: The motherboard finds no fan connected to the CPU_FAN header.
  
• CPU Fan Speed Too Low: The fan’s rotation is below the minimum RPM threshold.
  
• CPU Fan Error, Press F1 to Resume: The system halts booting until you confirm it is safe to proceed.

Each version points to the same problem, your system can’t detect steady fan movement or speed, so this warning shows up.

Why the Fan Error Appears During Startup:

This error appears when your system can not detect the CPU fan or its speed during startup. It is a built-in protection feature that prevents your processor from overheating or getting damaged. Common causes include:

• Loose or Incorrect Fan Connection: The fan is not plugged into the CPU_FAN header.
  
• Low Fan RPM: Quiet or high-performance fans sometimes spin below BIOS minimum limits.
  
• BIOS Misconfiguration: Incorrect fan speed thresholds or disabled monitoring causes wrong warnings.
  
• Dust or Physical Damage: Debris or worn bearings reduce fan efficiency.
  
• AIO Coolers: If the pump is on the wrong header, the motherboard assumes there is no fan.

Knowing these causes helps you find and fix the problem quickly, without risking your CPU.

Also Read: Can you Plug CPU Fan into System Fan? – Full Guide 2025!

How to Fix the CPU Fan Error on Boot?

To fix this startup fan problem, follow these trusted steps carefully. Each step targets a specific cause to help your PC boot normally again.

1.  Power off your PC and unplug it completely.
   
2. Open the case and check if the fan cable is connected to the CPU_FAN header.
   
3. Clean the fan blades and heatsink to remove dust or debris.
   
4. Boot into BIOS, open Hardware Monitor, and ensure the CPU fan is detected.
   
5. If the fan speed is too low, reduce or disable the CPU fan speed low limit BIOS setting to prevent false warnings.
   
6. Save BIOS settings, restart, and confirm that the error no longer appears.
   
7. If the problem continues, test with another fan or update your BIOS firmware.

These steps fix most PCs unless there is a serious hardware problem with the fan or motherboard.

Fix CPU Fan Error on ASUS, MSI, Gigabyte & ASRock:

Different motherboard brands report fan warnings in their own way. Knowing your motherboard’s BIOS path makes troubleshooting faster. Follow the step-by-step fixes below for each brand.

Fixing CPU Fan Error on ASUS Motherboards:

• Enter the BIOS, go to Monitor, and open Q-Fan Configuration.
  
• Set CPU Fan Speed Low Limit to Ignore or 200 RPM.
  
• Ensure the fan is connected to CPU_FAN.
  
• Save changes and reboot.

Fixing CPU Fan Error on MSI Boards:

• Go to BIOS, open Hardware Monitor, and select CPU Fan Control.
  
• Adjust CPU Fan Low Limit to Ignore.
  
• Save and exit BIOS, then restart.

Fixing CPU Fan Error on Gigabyte Boards:

• Open the BIOS, go to Smart Fan 5, and open Fan Control Settings.
  
• Adjust the fan speed threshold or disable the low limit warning.
  
• Check the fan connection to CPU_FAN.

Fixing CPU Fan Error on ASRock Boards:

• Enter the BIOS, open H/W Monitor, and go to CPU Fan 1 Setting.
  
• Reduce the low speed limit or choose Monitor only.
  
• Save and reboot the system.

Table for Quick Reference:

Brand	BIOS Path	Setting	Recommended Value
ASUS	Monitor and Q-Fan	CPU Fan Low Limit	Ignore / 200 RPM
MSI	Hardware Monitor	CPU Fan Low Limit	Ignore
Gigabyte	Smart Fan 5	Fan Threshold	Adjust / Disable
ASRock	H/W Monitor	CPU Fan 1	Monitor / Reduce

What Should You Do If You Are Using a Liquid Cooler AIO?

If you are using an AIO (All-in-One) liquid cooler, the CPU Fan Error on Boot often appears because the pump is not connected to the CPU_FAN header.

How to fix it properly:

• Check Connections: Plug your AIO pump cable into the AIO_PUMP or PUMP_FAN header, not CPU_FAN.
  
• Attach a Fan Temporarily: Connect any working fan to CPU_FAN so the motherboard can detect RPM.
  
• BIOS Settings: In the BIOS, open Monitor then Fan Settings, and set CPU Fan Speed to Ignore.
  
• Save & Restart: Exit BIOS and check if the error message is gone.

Pro Tip: If your BIOS supports it, set AIO_PUMP to run at full speed 100% for better cooling and stable performance.

You may also like: How to Check RAM Clearance with CPU Coolers? – Easy Guide 2025!

How to Check if Your CPU Fan Is Working Properly?

To make sure your CPU fan works properly and to avoid startup warnings, try these quick steps:

Visual Inspection:

Open your PC case and power on the system. Check if the fan spins smoothly without noise or vibration.

BIOS Hardware Monitor:

Enter the BIOS, go to Hardware Monitor, and look at the CPU Fan Speed (RPM). A healthy fan usually runs between 600 and 2000 RPM.

Software Tools (HWMonitor, SpeedFan, MSI Afterburner):

Use tools like HWMonitor, SpeedFan, or MSI Afterburner to track fan speed and CPU temperature in real time.

Best Visual Addition: Diagnostic Table

Fan Status	Possible Issue	Recommended Action
Not Spinning	Loose Connection	Reconnect the fan cable
Spinning Slowly	Dust or friction	Clean blades carefully
No RPM Detected	Wrong header	Move the cable to the CPU_FAN port
Noisy or Vibrating	Bearing damage	Replace the fan immediately

When and How to Replace Your CPU Fan?

You should replace your CPU fan when it starts showing clear signs of wear or reduced performance. A weak or failing fan can not keep your CPU cool, which may cause your PC to overheat or crash. Here is how to recognize the right time and replace it properly:

When to Replace:

• Grinding or rattling noises indicate worn bearings.
  
• The fan fails to spin during startup, suggesting motor failure.
  
• RPM drops below 300 or repeated BIOS warnings appear.

How to Replace:

• Power off and unplug your PC completely.
  
• Detach the old fan from the heatsink or cooler.
  
• Clean the heatsink surface and reapply thermal paste if necessary.
  
• Install the new fan securely and connect it to the CPU_FAN header.
  
• Boot the system and verify proper fan RPM in BIOS.

How to Stop the CPU Fan Error from Coming Back?

You can stop this warning from coming back by keeping your PC clean and well maintained. A few simple care steps can stop it for good.

• Clean Fans Regularly: Remove dust every few weeks to maintain airflow.
  
• Use Good Thermal Paste: Helps reduce CPU heat and fan stress.
  
• Update BIOS: Improves fan detection and speed control.
  
• Connect Fans Correctly: Always plug into the CPU_FAN header, not CHA_FAN.
  
• Cable Management: Keep cables clear from spinning fan blades.

Tip: Schedule a quick system check every month. It keeps temperatures low and performance stable.

Is It Safe to Ignore the CPU Fan Error on Boot?

No, ignoring the CPU Fan Error on Boot is not safe. This warning protects your CPU from overheating when the fan is not detected or spinning correctly. Running the system without cooling can cause heat damage or make it shut down automatically.

Always check your fan before disabling the alert in BIOS, unless you are using an AIO cooler with a separate pump connection.

Related: Is 4000 RPM Too Low for CPU Fan? – Optimize Cooling 2025!

What to Do If None of the Fixes Work?

If the fan warning still shows up after all fixes, the problem might be with the hardware or BIOS settings. Try these final solutions:

• Test the Fan: Connect it to another header or PC to confirm it works.
  
• Reset BIOS: Load default settings to clear incorrect fan configurations.
  
• Update BIOS: A newer version may fix fan detection issues.
  
• Replace Fan or Header: If either is damaged, replace the faulty part.
  
• Contact Support: If nothing helps, reach out to your motherboard manufacturer.

Expert Tip: Try another fan or cooler to check if the problem is with the fan or the motherboard.

FAQs:

Conclusion:

The CPU Fan Error on Boot is usually caused by loose connections, low fan speed, or BIOS settings. Following these step-by-step fixes ensures your CPU stays cool and your system runs smoothly. Regular maintenance and monitoring prevent future errors, keeping your PC safe and reliable.