Laptop Fan Running Constantly or Making Noise — How to Diagnose and Quiet It

Overview #

A laptop fan that runs continuously or makes loud grinding or clicking noises indicates that the cooling system is working under stress or partially failing.
Common causes include high background CPU usage, dust buildup, misapplied thermal paste, or a failing fan bearing.
This guide walks you through verifying temperatures, identifying the cause, and restoring quiet, normal operation.

What you’ll learn

• How to monitor fan speeds and system temperatures
• How to clean or recalibrate the cooling system
• How to identify software or background processes causing overheating
• How to reset firmware power control for fan stability

Estimated time: 20–30 minutes
Skill level: Intermediate

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Terms and Definitions #

Term	Meaning
RPM	Revolutions per minute, the speed of the cooling fan
SMC (System Management Controller)	Chip managing thermal and power functions on Mac
Thermal paste	Material that improves heat transfer between CPU/GPU and heat sink
Idle temperature	Normal CPU temperature when the computer is not under load (typically 40–55°C)

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Steps #

Step 1 — Observe Fan Behavior #

1. Listen to the fan’s tone: constant high-speed noise indicates thermal load or stuck control signal.
2. Check if the fan ramps up immediately after startup (before loading apps).
3. If it remains loud even in BIOS or Recovery Mode, it is a hardware or sensor issue rather than software.

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Step 2 — Monitor Temperatures #

Windows PowerShell

Get-WmiObject MSAcpi_ThermalZoneTemperature | Select-Object CurrentTemperature

Divide the reported value by 10 and subtract 273 to convert to Celsius.
Example: 3200 = 47°C.

macOS Terminal

sudo powermetrics --samplers smc | grep "CPU die temperature"

Shows CPU die temperature in Celsius.
Ideal idle temperature: 40–55°C.
If the temperature exceeds 85°C for extended periods, inspect cooling components.

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Step 3 — Identify High CPU or GPU Usage #

Windows PowerShell

Get-Process | Sort-Object CPU -Descending | Select-Object -First 10

Lists the top ten processes consuming the most CPU time.

macOS Terminal

top -l 1 | head -n 15

Displays active processes and their CPU percentage.

If the fan increases speed only when certain applications run, software load is the cause.
Terminate or update those processes before proceeding.

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Step 4 — Check Background and Startup Processes #

Windows PowerShell

Get-CimInstance Win32_StartupCommand | Select-Object Name, Command

Lists programs that automatically launch during startup.
Disable unnecessary entries through Task Manager → Startup tab.

macOS

osascript -e 'tell application "System Events" to get the name of every login item'

Shows startup applications.
Remove unnecessary items from System Settings → General → Login Items.

Fewer background programs mean lower CPU load and quieter fan speeds.

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Step 5 — Verify Fan and Sensor Operation #

Windows
Install OpenHardwareMonitor or HWiNFO to check actual RPM values.
If the fan shows 0 RPM while clearly spinning, the tachometer signal or sensor may be failing.

macOS Terminal

sudo powermetrics --samplers smc | grep Fan

Displays current fan speeds.
Typical range: 2000–4000 RPM under load.
Values above 5000 RPM indicate heavy thermal stress or runaway control.

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Step 6 — Clean Air Vents and Fans #

1. Power off and unplug the computer.
2. Use compressed air to blow out vents gently.
3. Avoid spinning the fan blades at high speed—hold them stationary while cleaning.
4. For heavily used systems, remove the bottom panel and clear dust from the heat sink and exhaust channels.

Dust buildup is the most common cause of persistent fan noise and heat.

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Step 7 — Reset Power and Thermal Control #

Windows (Embedded Controller reset)

1. Shut down completely.
2. Disconnect charger and battery (if removable).
3. Hold Power for 15 seconds to discharge residual energy.
4. Reconnect power and restart.

macOS (SMC reset)

1. Shut down.
2. Hold Shift + Control + Option + Power for 10 seconds.
3. Release and power on.

This reset clears stored fan calibration and restores default speed control.

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Step 8 — Check for Firmware or Driver Updates #

Windows PowerShell

Get-WmiObject Win32_BIOS | Select-Object SMBIOSBIOSVersion, ReleaseDate

Check your manufacturer’s support site for newer BIOS or firmware versions.
Many laptop vendors release fan curve and power-management updates.

macOS

softwareupdate -l
softwareupdate -i -a

Apple distributes SMC and thermal updates through standard system updates.

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Step 9 — Reseat Thermal Components (Advanced) #

If cleaning and resets fail, the CPU and GPU may have degraded thermal paste.

1. Remove the heat sink carefully.
2. Clean the old compound with isopropyl alcohol (90% or higher).
3. Apply a thin layer of high-quality thermal paste.
4. Reinstall the heat sink securely.

This procedure can reduce temperatures by 5–10°C but should be performed only if you’re comfortable with hardware disassembly.

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Verification #

Check	Command	Expected Result
Temperature	Get-WmiObject MSAcpi_ThermalZoneTemperature	40–55°C idle, <80°C under load
Fan speed	powermetrics --samplers smc	2000–3500 RPM normal
CPU load	Get-Process or top	Low when idle
Noise level	Observation	Fan cycles down after 1–2 minutes idle

If all readings are within these ranges and noise stabilizes, the system is operating correctly.

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Conclusion #

A constantly running or noisy fan almost always results from either excess heat or blocked airflow.
By monitoring temperatures, removing dust, updating firmware, and resetting the power controller, most users can restore quiet operation without hardware replacement.
If the fan remains noisy even at cool temperatures, its bearing may be worn and the fan assembly should be replaced.