If the fan on your MacBook Pro is constantly running even when you’re not doing anything demanding, it could be a sign of a few different issues. The fan is designed to turn on when the Mac needs to cool down the CPU and internal components, so if it’s always on, something is causing the system to heat up. Here are some common reasons why the fan may be constantly spinning and some steps you can take to fix it.
Too many apps and browser tabs open
The most common reason for an overactive fan is having too many apps and browser tabs running at once. The more applications and services running, the harder the CPU has to work, generating more heat. Try closing any apps you aren’t actively using and minimizing the number of browser tabs open to see if that makes a difference.
Apps like Slack, Mail, Calendar, Music, Photos, etc. that run in the background can gradually heat up the system over time. Quit or disable any non-essential background apps to reduce CPU load. You can use Activity Monitor to see which apps and processes are using up the most resources.
Outdated software and OS
Running outdated software can also cause excess fan activity. Make sure you’re updated to the latest versions of macOS, apps, browser plugins, etc. Older versions tend to be less optimized and may work the CPU harder. Keep your operating system and software updated to benefit from performance improvements and bug fixes.
In particular, be sure to install all available macOS updates, which often include fan and thermal management fixes. Go to System Preferences > Software Update to check for updates. Having the latest OS optimizations goes a long way in keeping fan usage reasonable.
Hardware-intensive tasks
Using processor-intensive software like video editors, 3D rendering apps, VR software, or even a very large spreadsheet can make the fans kick into high gear. The fans are just doing their job of keeping the Mac cool under heavy load. Don’t worry too much about temporary fan usage while performing taxing operations.
Keep in mind that some tasks like rendering video or exporting huge images use a lot of sustained CPU power. It may take a while for the fans to spin back down after completing the heavy job. Give it some time to cool off before assuming there’s an underlying problem.
Dust buildup
Dust, pet hair, and other particles can accumulate and block the MacBook Pro’s cooling vents over time. This restricts airflow and reduces the fans’ ability to cool the computer. If the vents are covered, the fans will spin faster trying to maintain the target system temperature.
Carefully use compressed air to blow out any vents and heat sinks that have noticeable dust buildup. Be sure to follow Apple’s instructions to avoid damaging sensitive components. Avoid blowing air directly at the fan blades and don’t use a vacuum. With the vents cleared, the fans should be able to cool better at lower speeds.
High room temperature
If you’re using your MacBook Pro in a hot environment, the fans will need to work harder to keep temps down. Check that the ambient room temperature isn’t too high. Aim to keep surrounding temps between 50-95°F (10-35°C) for optimal performance.
Make sure ventilation intakes aren’t blocked by bedding, tablecloths, or other fabrics when used on soft surfaces. Leaving enough clearance for airflow can help. If possible, use the Mac in cooler rooms and avoid direct sunlight heating things up.
Faulty temperature sensors
The MacBook Pro uses a network of temperature sensors to determine if and how fast to spin the fans. If the sensors malfunction and report false high temps, the fans may be triggered when they’re not actually needed.
Resetting the SMC can help recalibrate sensor readings. First fully shut down the MacBook, then press Shift-Control-Option on the left side of the keyboard and the power button at the same time. Hold for 10 seconds to reset before turning it back on. This may resolve any incorrect sensor data.
High CPU usage in sleep
Some apps can cause the CPU to ramp up while the computer is sleeping, which will immediately wake it and turn on the fans. This often points to an app that has some runaway process or memory leak occurring in the background.
Open Activity Monitor and sort by CPU usage to identify any processes using high resources when you aren’t actively using the Mac. Quit or uninstall any problematic apps, or use a tool like App Tamer to force them to behave better in the background.
Excessive Chrome tabs
Google Chrome is somewhat notorious for sluggish performance and battery drain compared to other browsers. Having many Chrome tabs open, especially with Flash content, can really heat up the CPU and cause the fans to remain active.
Try closing Chrome entirely and switching to Safari or Firefox to see if that helps. Limit Chrome tabs to only what you’re actively using. Avoid Flash and beware of Chrome extensions that run in the background. Chrome may simply need more resources than other browsers.
Noisy, worn, or faulty fan
In some cases, the fans may be running loudly or constantly simply because they are getting old and worn or have developed an issue. Over time, fan bearings can wear out or get clogged with dust, causing noticeable noise or changes in function.
Listen closely to isolate the fan sound and see if it seems to be coming from a faulty fan. Try stopping the fans briefly with an app like Macs Fan Control. If noises or high speeds continue when fans are stopped, it points to a bad fan.
If one or more fans appear to not be working correctly, they may need to be repaired or replaced. Your best bet is to take it to an Apple store or authorized service provider for assessment.
External dust or pet hair around vents
Even if you’ve cleaned the internal vents, external dust buildup around the exhaust vents along the back hinge can also cause issues. Pet hair and lint around the outside vents can obstruct normal airflow.
Carefully use compressed air or a soft brush to remove any debris around the outside vents. Also check any case or cover you use regularly to make sure it’s not trapping material near the vents over time. Keep the back hinge area free of clutter.
Faulty thermal paste application
The thermal paste applied between the CPU chip and heat sink can dry out or become insufficient over time. This paste helps transfer heat from the CPU to the heat sink. If the layer of paste has an issue, heat gets trapped at the CPU and fans compensate by spinning faster.
Checking the condition of the thermal paste requires opening up the MacBook Pro to inspect the CPU connection. If you’re comfortable doing so, you can replace the paste yourself following a guide. Otherwise, a repair shop can replace it for you for the best results.
Malfunctioning fans
If a fan completely stops spinning or becomes “stuck” at a certain RPM, the other functioning fans will ramp up to compensate. Listen closely to each fan or use a utility like Macs Fan Control to isolate any fans not behaving properly.
Fans can become stuck if dust/debris clogs the blades or bearings. Other times the motor or controller just fails. Replace any non-functional fans as soon as possible to restore normal operation and prevent other fans from overworking.
High ambient heat
If you use your MacBook Pro while it’s sitting directly on a bed, couch, or other soft surface, this can block airflow through the bottom vents. The underside of the laptop should have open airflow for optimal cooling.
Try placing your Mac on a hard surface like a desk or table instead of direct fabric contact. This allows better airflow and reduces operating temperature for less fan usage. Avoid blocking the bottom vents to prevent heat buildup internally.
Clogged heat sink fins
The heat sink fins inside the MacBook Pro can accumulate dust and debris over time. Clogged fins prevent heat from properly dissipating away from the CPU, causing internal temps to rise.
Carefully use compressed air to clear out any dusty material between the fins and around the heat sink. Be sure not to damage any small components with the air blast. Properly cleaning the heat sink fins should allow the fans to cool the CPU more efficiently.
Conclusion
An overworked MacBook Pro fan often points to overheating issues caused by system load, dusty vents, or other environmental factors. Try troubleshooting software and apps first, then consider cleaning internal and external vents if needed. Faulty fans or sensors could also be the culprit. Getting to the root cause allows you to remedy constant fan spin for a cooler and quieter Mac.