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How to Fix a Mac that Randomly Shuts Off

Authored by:
Support.com Tech Pro Team
This Guided Path® was written and reviewed by Support.com’s Tech Pro team. With decades of experience, our Tech Pros are passionate about making technology work for you. We love feedback! Let us know what you think about this Guided Path® by rating it at the end.

Introduction

Sometimes you may experience your Mac to abruptly shut off while performing your daily tasks. This can be frustrating especially if it's happening repeatedly.

This guide will take you through some troubleshooting steps that may help fix this issue. The steps are listed in order, so start with the first one, see if that helps, and then continue with the next one if it doesn't.

iMac

1 Check the Mac's Power Connection

Make sure the Mac is powered up properly by checking the electrical connections.

  1. Make sure you are using a working electrical outlet. You can test another electric device, such as a lamp, with the same outlet. Bypass any power strips for troubleshooting purposes.
    Lamp outline.
  2. Make sure the power connections to and from the Mac are proper. Choose the type of Mac you have below.
    MacBook

    There are two ways to power up a MacBook:

    • Using the power supply without the extension cord:
      MacBook being connected to power with power supply without extension cord.
      1. Examine the cable and connectors for visible damage. If they are damaged, they may need to be replaced.
      2. Make sure the power supply is firmly plugged into the power socket and power connector into the computer.
    • Using the power supply with the extension cord:
      MacBook being connected to power with power supply with extension cord.
      1. Examine all cables and connectors for visible damage. If they are damaged, they may need to be replaced.
      2. Make sure the power supply is firmly plugged into the power socket, the extension cord into the power supply and power connector into the computer.
    • The power adapter shapes and way of connecting them have stayed the same over the years, however the connector types that plug into the computer have changed somewhat and can be of the following types:
      1. Magnetic T style
      2. Magnetic L style
      3. USB-C style

      Different types of MacBook power connectors.
    iMac
    1. An iMac is powered up by plugging it in directly into a power socket.
      iMac being connected to power.
    2. Examine the cable and connectors for visible damage. If they are damaged, they may need to be replaced.
    3. Make sure one end is firmly plugged into the back panel of the iMac and the other end into a power socket.
    Mac Pro
    1. A Mac Pro has an internal power supply included in the case.
    2. The power cable looks like below. Examine the cable and connectors for visible damage. If you find any damage, the cable may need to be replaced.
      Mac Pro power cable.
    3. Make sure one end of the cable is firmly plugged into a wall outlet.
    4. Make sure the other end is firmly plugged into the power socket on the rear side of the case.
      Power socket highlighted on rear side of Mac Pro.
    Mac Mini

    Mac Mini with internal power supply

    1. Some Mac Mini computers have an internal power supply:
      • One connector (1) plugs into the computer
      • The other connector (2) plugs into a power socket
      Mac Mini being plugged into power.
    2. Examine all cables and connectors for visible damage. If they are damaged, they may need to be replaced.
    3. Make sure all connectors are firmly plugged in.

    Mac Mini with external power supply

    1. Other Mac Mini computers have an external power supply and plugs in like below:
      • One connector (1) plugs into the computer
      • The other connector (2) plugs into a power socket
      • A third (3) connector plugs into the supply itself
      Mac Mini being connected to power.
    2. Examine all cables and connectors for visible damage. If they are damaged, they may need to be replaced.
    3. Make sure all connectors are firmly plugged in.

2 Check the Computer's Ventilation

Computers heat up while they're running and their internal parts need to be cooled down and kept at a certain temperature to perform optimally. If the computer overheats it may result in it shutting down to prevent damage to its components. In worst cases, the components may also melt or get fried if the computer is kept running at a high temperature. To check whether your computer still has working fans, try the following:

  1. Look for any vents your computer may have: in the back, on the side or bottom.
    Vents pointed out on read of desktop PC.
    Vents pointed out on side of laptop.
  2. With the computer turned on, place your hand in front of the vents and feel if there is any air blowing.

    The longer the computer is turned on and the more complex the tasks it needs to perform, the warmer and stronger the air flow should be.

  3. Depending on your results, you will have three options:
    • There is no air blowing – This could mean the fans are not working and the computer has no cooling.

      Please contact the product manufacturer for further assistance.

    • The air flow feels weak – The computer's fans may have dirt built up on and inside them which is causing them to slow down and not blow enough air to properly cool down the internal components. This can be fixed by cleaning up the outside and inside of the computer, and oiling up the fans.
    • The air flow feels normal – This could mean the issue the computer is having is software related. There are a few different software fixes that may be attempted to resolve the issue.

3 Clean the Computer's Vents

If you had a computer for more then a few months, it is likely to have accumulated some dirt inside and out. Dust, grime, hair and other debris can build up on fans, heatsinks and other parts. Components can also come loose or become unseated over time. All these can affect a computers performance in a negative way.
Dust buildup inside a computer.

This is a generic method on how to clean the vents for any type of computer. If your computer looks differently than the one represented in the picture below, the steps you need to follow are exactly the same.

Using a compressed air duster is the best and most recommended way of cleaning a computers vents.

When blowing compressed air, keep the can upright at all times and never shake it to prevent the liquid refrigerant from leaking onto your electronics. Use short bursts of two or three seconds. When the can gets too cold to hold, set it down for a few minutes until it warms up again.

  1. Turn the computer off and unplug its power cable.
  2. Locate the air vents or other openings.
  3. Blow compressed air to clean up the vents or other openings.
    Using gas duster to clean laptop vents.
  4. Once done, reconnect the power cable and turn the computer on to test it out.

If the Computer Is Still Overheating

Please contact the product manufacturer for further assistance.

4 Check for Updates

  1. Select the Apple menu, then App Store.
    macOS Mojave Apple Menu with App Store highlighted.
  2. You will now see the app store pull up. Select Updates.
    If Your Mac is Running 10.14 Mojave or Later App Store side bar with Updates highlighted.
    If Your Mac is Running 10.13 High Sierra or Earlier App store menu bar with Updates highlighted.

Any version of macOS 10.7 (Lion) or older can check for available updates through the Apple Menu and Software Updates.

5 Reinstall macOS

When you've exhausted all options in trying to fix a major issue with your Mac computer, you may be left with having to reinstall macOS to bring it to its original state it was in out of the box.

Reinstalling macOS will remove all customization, files, and programs on your computer. Make sure you have a recent backup before proceeding.

Back Up All Personal Data
  1. Select Apple Menu > Restart.
    macOS Mojave Apple Menu with Restart highlighted.
  2. Immediately after your Mac restarts (some Mac computers play a startup sound), press and hold the command ⌘ and R keys until the Apple logo appears, then release the keys.
    Mac keyboard with command and R keys highlighted
  3. Highlight Reinstall macOS, then select Continue.
    macOS Utilities with Reinstall macOS and Continue button highlighted
  4. macOS setup will begin. Select Continue.
    macOS Install with Continue highlighted.
  5. Select Agree to accept the Terms of Service.
    macOS Terms of service with Agree highlighted.
  6. Select Agree to confirm you agree with Terms of Service.
    Terms of Service dialog with Agree highlighted.
  7. Choose a Drive to install macOS on and select Install.
    macOS install drive selection with drive and Install highlighted.
  8. Install will now start and this will take some time. The computer will reboot during this process.

If the Issue Persists

Please contact the product manufacturer for further assistance.

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Sometimes you may experience your Mac to abruptly shut off while performing your daily tasks. This can be frustrating especially if it's happening repeatedly.

This guide will take you through some troubleshooting steps that may help fix this issue. The steps are listed in order, so start with the first one, see if that helps, and then continue with the next one if it doesn't.

iMac

Make sure the Mac is powered up properly by checking the electrical connections.

  1. Make sure you are using a working electrical outlet. You can test another electric device, such as a lamp, with the same outlet. Bypass any power strips for troubleshooting purposes.
    Lamp outline.
  2. Make sure the power connections to and from the Mac are proper. Choose the type of Mac you have below.
    MacBook

    There are two ways to power up a MacBook:

    • Using the power supply without the extension cord:
      MacBook being connected to power with power supply without extension cord.
      1. Examine the cable and connectors for visible damage. If they are damaged, they may need to be replaced.
      2. Make sure the power supply is firmly plugged into the power socket and power connector into the computer.
    • Using the power supply with the extension cord:
      MacBook being connected to power with power supply with extension cord.
      1. Examine all cables and connectors for visible damage. If they are damaged, they may need to be replaced.
      2. Make sure the power supply is firmly plugged into the power socket, the extension cord into the power supply and power connector into the computer.
    • The power adapter shapes and way of connecting them have stayed the same over the years, however the connector types that plug into the computer have changed somewhat and can be of the following types:
      1. Magnetic T style
      2. Magnetic L style
      3. USB-C style

      Different types of MacBook power connectors.
    iMac
    1. An iMac is powered up by plugging it in directly into a power socket.
      iMac being connected to power.
    2. Examine the cable and connectors for visible damage. If they are damaged, they may need to be replaced.
    3. Make sure one end is firmly plugged into the back panel of the iMac and the other end into a power socket.
    Mac Pro
    1. A Mac Pro has an internal power supply included in the case.
    2. The power cable looks like below. Examine the cable and connectors for visible damage. If you find any damage, the cable may need to be replaced.
      Mac Pro power cable.
    3. Make sure one end of the cable is firmly plugged into a wall outlet.
    4. Make sure the other end is firmly plugged into the power socket on the rear side of the case.
      Power socket highlighted on rear side of Mac Pro.
    Mac Mini

    Mac Mini with internal power supply

    1. Some Mac Mini computers have an internal power supply:
      • One connector (1) plugs into the computer
      • The other connector (2) plugs into a power socket
      Mac Mini being plugged into power.
    2. Examine all cables and connectors for visible damage. If they are damaged, they may need to be replaced.
    3. Make sure all connectors are firmly plugged in.

    Mac Mini with external power supply

    1. Other Mac Mini computers have an external power supply and plugs in like below:
      • One connector (1) plugs into the computer
      • The other connector (2) plugs into a power socket
      • A third (3) connector plugs into the supply itself
      Mac Mini being connected to power.
    2. Examine all cables and connectors for visible damage. If they are damaged, they may need to be replaced.
    3. Make sure all connectors are firmly plugged in.

Computers heat up while they're running and their internal parts need to be cooled down and kept at a certain temperature to perform optimally. If the computer overheats it may result in it shutting down to prevent damage to its components. In worst cases, the components may also melt or get fried if the computer is kept running at a high temperature. To check whether your computer still has working fans, try the following:

  1. Look for any vents your computer may have: in the back, on the side or bottom.
    Vents pointed out on read of desktop PC.
    Vents pointed out on side of laptop.
  2. With the computer turned on, place your hand in front of the vents and feel if there is any air blowing.

    The longer the computer is turned on and the more complex the tasks it needs to perform, the warmer and stronger the air flow should be.

  3. Depending on your results, you will have three options:
    • There is no air blowing – This could mean the fans are not working and the computer has no cooling.



    • The air flow feels weak – The computer's fans may have dirt built up on and inside them which is causing them to slow down and not blow enough air to properly cool down the internal components. This can be fixed by cleaning up the outside and inside of the computer, and oiling up the fans.
    • The air flow feels normal – This could mean the issue the computer is having is software related. There are a few different software fixes that may be attempted to resolve the issue.

If you had a computer for more then a few months, it is likely to have accumulated some dirt inside and out. Dust, grime, hair and other debris can build up on fans, heatsinks and other parts. Components can also come loose or become unseated over time. All these can affect a computers performance in a negative way.
Dust buildup inside a computer.

This is a generic method on how to clean the vents for any type of computer. If your computer looks differently than the one represented in the picture below, the steps you need to follow are exactly the same.

Using a compressed air duster is the best and most recommended way of cleaning a computers vents.

When blowing compressed air, keep the can upright at all times and never shake it to prevent the liquid refrigerant from leaking onto your electronics. Use short bursts of two or three seconds. When the can gets too cold to hold, set it down for a few minutes until it warms up again.

  1. Turn the computer off and unplug its power cable.
  2. Locate the air vents or other openings.
  3. Blow compressed air to clean up the vents or other openings.
    Using gas duster to clean laptop vents.
  4. Once done, reconnect the power cable and turn the computer on to test it out.

If the Computer Is Still Overheating

  1. Select the Apple menu, then App Store.
    macOS Mojave Apple Menu with App Store highlighted.
  2. You will now see the app store pull up. Select Updates.
    If Your Mac is Running 10.14 Mojave or Later App Store side bar with Updates highlighted.
    If Your Mac is Running 10.13 High Sierra or Earlier App store menu bar with Updates highlighted.

Any version of macOS 10.7 (Lion) or older can check for available updates through the Apple Menu and Software Updates.

When you've exhausted all options in trying to fix a major issue with your Mac computer, you may be left with having to reinstall macOS to bring it to its original state it was in out of the box.

Reinstalling macOS will remove all customization, files, and programs on your computer. Make sure you have a recent backup before proceeding.

Back Up All Personal Data
  1. Select Apple Menu > Restart.
    macOS Mojave Apple Menu with Restart highlighted.
  2. Immediately after your Mac restarts (some Mac computers play a startup sound), press and hold the command ⌘ and R keys until the Apple logo appears, then release the keys.
    Mac keyboard with command and R keys highlighted
  3. Highlight Reinstall macOS, then select Continue.
    macOS Utilities with Reinstall macOS and Continue button highlighted
  4. macOS setup will begin. Select Continue.
    macOS Install with Continue highlighted.
  5. Select Agree to accept the Terms of Service.
    macOS Terms of service with Agree highlighted.
  6. Select Agree to confirm you agree with Terms of Service.
    Terms of Service dialog with Agree highlighted.
  7. Choose a Drive to install macOS on and select Install.
    macOS install drive selection with drive and Install highlighted.
  8. Install will now start and this will take some time. The computer will reboot during this process.

If the Issue Persists