Why wont my Mac fan turn off?

It can be frustrating when your Mac’s internal cooling fans run constantly or turn on more frequently and loudly than usual. A noisy, constantly spinning fan is not only annoying but can indicate larger issues with your computer. Here are some quick answers to common questions about Mac fans that won’t turn off, along with more detailed troubleshooting tips to help diagnose and resolve the problem.

Quick Answers

Why does my Mac’s fan keep running?

The most common reasons a Mac’s fans run constantly or won’t turn off are:

  • Overheating – The fans are trying to cool down an overheated CPU or internal components.
  • Dust buildup – Dust and debris have accumulated and are blocking airflow.
  • Software issue – An app or process is consuming a lot of CPU resources.
  • Hardware problem – There is an issue with a temperature sensor or fan control component.

How can I get my Mac’s fan to be quieter and turn off?

Try these troubleshooting steps:

  1. Clean dust buildup from inside the Mac and fans.
  2. Quit CPU or GPU intensive apps and processes.
  3. Check Activity Monitor for any app or process using high CPU.
  4. Reset the SMC and PRAM/NVRAM.
  5. Reapply thermal paste between the CPU and heatsink.
  6. Use a fan control app to adjust fan speeds.

Should I be concerned if my Mac’s fans run constantly?

Frequently spinning fans indicate your Mac is overworking to maintain safe internal temperatures. Prolonged high heat can damage components and cause performance issues or crashes. Diagnose and address the underlying cause as soon as possible.

Common Causes of Mac Fans Running Constantly

If your Mac’s cooling fans are constantly spinning even at idle, or ramp up in speed very frequently, there are a several common culprits to blame:

Overheating from High CPU/GPU Usage

The most common trigger for Mac fans running nonstop is overheating from CPU or GPU intensive tasks. Things like gaming, video editing, rendering, compiling code, or processing large files can make the fans work overtime to keep the internals cool.

Check Activity Monitor to see if there are any apps or processes hogging system resources. Quit or force quit them to allow the computer to cool down and the fans to decrease speed.

Dust Buildup Blocking Airflow

Fans help keep your Mac cool by exchanging internal hot air for cooler external air. But over time, dust accumulation inside the computer can clog cooling vents, fans, heat sinks, and airflow channels. With airflow obstructed, fans spin faster in an attempt to compensate.

Carefully cleaning built up dust from inside your Mac can remove the obstruction and allow fans to return to normal speeds. Use a can of compressed air to blow out vents. If needed, open up the computer to directly clean fans and internal components.

Software Issue or Runaway Process

Sometimes a software glitch or runaway process can cause massive CPU usage spikes that heat up your Mac and trigger the fans. Look in Activity Monitor for any process using an abnormal amount of CPU resources and force quit it.

Reboot your computer and check if fans still run constantly. If the issue persists after a restart it may be an inherent problem with a particular software program.

Problem with Hardware Temperature Sensors

Macs use a number of onboard thermal sensors to track temperatures in different areas like the CPU, GPU, power supply, etc. Faulty temperature input can confuse the Mac’s cooling system and cause fans to run when they shouldn’t.

Use an app like Macs Fan Control to view all of your Mac’s temperature sensor data. If you see unusual readings from one or more sensors it may indicate a hardware issue.

Issue with Fan Control Mechanism

The system which controls your Mac’s fan speeds can malfunction causing constant fan operation. The SMC (System Management Controller) regulates fan activity based on thermal data. A damaged or failing SMC can get stuck constantly signaling fans to run at high speed.

Reset both the SMC and NVRAM on your Mac to see if it resolves a fan control problem. If not, it indicates a deeper hardware or firmware bug may need repair.

How to Diagnose Mac Fan Issues

Use the following steps to get to the root of why your Mac’s fans are misbehaving and won’t turn off:

1. Monitor CPU and GPU Usage

Open Activity Monitor in the Utilities folder and sort processes by CPU usage. Look for anything using a very high percentage of resources. Also check the Energy tab to see if either the CPU or GPU graph is spiking frequently.

Quit or force quit apps and processes putting excessive load on your components. This may immediately resolve overactive fans if an app is causing overheating.

2. Check for Thermal Throttling

Overburdened, overheating components can be thermally throttled by your Mac. This reduces power to maintain safe temperatures, but results in performance drops.

Apps like iStat Menus can show when CPU or GPU throttling occurs. If you see regular throttling events, overheating is likely causing the nonstop fan activity.

3. Monitor Fan Speeds

Use a utility like Macs Fan Control to see current fan speeds and get alerts for abnormal behavior. Check if fans are ramping up and down frequently or stuck running at high RPMs. This can help narrow down fan issues.

4. Examine Temperature Sensors

With a tool like iStat Menus, inspect temperature sensor readings including the CPU, GPU, power supply, ambient air, and more. Look for any unusual spikes or temperatures outside expected ranges which could trigger fan activity.

5. Test with Clean User Account

Log into a fresh, clean user account with no apps installed. See if fans still behave erratically even when no user apps or processes are running. This indicates a deeper system issue, not something isolated to your main account.

6. Check for Unusual Background Activity

Use Activity Monitor to sort processes by CPU usage, then inspect what’s running in the background when your Mac is idle. Look for anything unfamiliar or system processes using more resources than expected. This can help uncover problematic software triggering fans.

7. Scan for Malware

Run a malware scan using built-in tools like XProtect or a third party antivirus app. Crypto mining malware and other infections can overload a Mac with background activity resulting in overheating fans.

How to Fix Mac Fans That Won’t Stop Running

Once you’ve diagnosed the probable cause of constantly running Mac fans, try these fixes to resolve the issue:

Clean Dust Buildup from Inside the Mac

Carefully blow out any accumulated dust from the Mac’s vents, fans, heat sinks and internal components using compressed air. Also replace any clogged air filters. This removes airflow obstructions that can cause overheating.

Manage Intensive Apps Causing Overheating

Adjust settings in apps like Final Cut Pro and Photoshop to reduce resource usage. Or avoid running sustained demanding tasks during hot weather or with the Mac on your lap, both of which can block airflow.

Reapply Thermal Paste on the CPU

Old, dried out thermal paste between the CPU chip and heat sink reduces heat dissipation, potentially causing overheating. Reapplying high quality thermal paste can lower temperatures.

Reset SMC and NVRAM

Resetting your Mac’s SMC and NVRAM can clear out any corrupted power and hardware management data that could be mistakenly triggering fans. This commonly fixes fan control issues.

Use a Fan Control App

Apps like Macs Fan Control let you manually adjust fan speeds. Override erratic fan behavior by setting custom RPM levels for cooling and quiet operation.

Avoid Blocking Airflow Near the Mac

Ensure your Mac has open, unobstructed access to outside airflow all around it. Don’t place on soft surfaces like beds, sofas or laps which can block vents.

Get a Computer Repair

For hardware sensor or fan control problems, take your Mac to Apple or an authorized repair center. They can diagnose issues with components and firmware and replace any defective parts.

Tips to Prevent Mac Fan Problems

Use the following best practices to avoid excessive, annoying fan noise and keep your Mac running cool and quietly:

  • Clean dust buildup from your Mac regularly using compressed air.
  • Don’t block airflow around your Mac and elevate it if using on a soft surface.
  • Monitor CPU/GPU usage and beware of overheating from intensive tasks.
  • Keep your Mac up to date with the latest macOS updates.
  • Use a laptop cooling pad, stand or ventilated case.
  • Configure power settings to reduce energy usage and heat output.
  • Repaste the CPU and GPU every few years or when replacing components.
  • Listen for changes in fan behavior and troubleshoot issues early.


Macs rely on internal cooling fans to prevent critical components like the CPU and GPU from overheating. Fans that constantly run or never turn off are annoying but also a sign something is wrong with your computer.

With some targeted troubleshooting and the right repairs, you can likely resolve a Mac’s fans that won’t stop spinning. Just be sure to address the problem sooner than later, as prolonged overheating can irrevocably damage your Mac.