Apple Silicon iMac: Power and Startup Issues
Troubleshooting intermittent shutdown or system instability
Troubleshooting startup issues
Troubleshooting intermittent shutdown or system instability
Identify issues
Read these articles if you notice any of the following issues:
The computer shuts down during startup
The computer shuts down unexpectedly during use
The computer restarts and displays an alert message
The computer doesn't respond after startup
The computer doesn't respond after waking from sleep
The computer has slow performance
If your Mac doesn't start up all the way
If your Mac restarted because of a problem
If the issue wasn’t resolved by following a support article, continue to the next section.
Try quick troubleshooting steps
Collect the following information:
When the computer shuts down (for example, on battery power or after running for a while)
How frequently the computer shuts down
Which applications are running at the time
How easy it is to cause the computer to shut down
Inspect the computer for liquid damage. Contact with liquid can short internal circuits and cause fans to stop working.
Run manual and diagnostic tests
If the issue wasn’t resolved by following a support article or checking for potential causes, run these diagnostic and manual tests to help isolate the cause of the issue:
Attempt to start up in Safe Mode to verify that the computer can start up completely without any issues.
Run the Mac Resource Inspector (MRI) diagnostic suite.
Note: This test will gather diagnostic information and verify that thermal sensor readings are within limits. Check MRI results for any power, fan, or thermal warnings or failures.
Open and inspect the computer
If the issue wasn’t resolved or isolated by following support articles or running diagnostics tests, refer to the computer's repair manual to open and inspect the computer. A damaged or out-of-place part may be causing one of the issues.
Follow repair manual procedures to open the computer.
Inspect internal components and the enclosure for indications of physical or liquid damage, contamination, or burned or darkened areas.
Inspect the area around the heat sink and each fan for dust or debris. Use an ESD-safe vacuum or compressed air to carefully remove dust and debris from the heat sink and fans. Ensure that each fan spins freely and is not obstructed.
Note: This section requires ordering parts and tools. Replacing a part may not resolve the device’s issue. You can find other service options at support.apple.com/repair.
Replace the part
If the issue wasn’t resolved or isolated by following the previous steps, replace the logic board.
Note: This section requires ordering parts and tools. Replacing a part may not resolve the device’s issue. You can find other service options at support.apple.com/repair.
Troubleshooting startup issues
Identify issues
Read these articles if you notice any of the following issues:
The computer doesn’t start up completely when it’s turned on
The display shows an icon of an exclamation point inside a circle
The computer initially appears to be turned off but shows signs of power, such as a spinning fan
If your Mac doesn't start up all the way
If your Mac restarted because of a problem
If your Mac starts up to an exclamation point in a circle
If your Mac starts up to Options with a gear icon
If you can't start up from macOS Recovery
Use macOS Recovery on a Mac with Apple silicon
If the issue wasn’t resolved by following a support article, continue to the next section.
Try quick troubleshooting steps
Inspect the computer for liquid damage. Contact with liquid can short internal circuits and cause fans to stop working.
Run manual and diagnostic tests
If the issue wasn’t resolved by following a support article or checking for potential causes, run these diagnostic and manual tests to help isolate the cause of the issue:
Determine whether the computer has power by confirming any of the following:
The built-in display functions
A fan spins
A connected external display functions
If the computer shows no indications of power, refer to troubleshooting no power.
Attempt to start up in Safe Mode to verify that the computer can start up completely without any issues.
Connect a compatible external display to the computer. Check for an image on the connected external display.
Attempt to start up the computer to macOS Recovery. Verify that the computer starts up to macOS Recovery.
While started up to macOS Recovery, use Disk Utility to verify the computer’s internal startup volume. If you notice errors, use Disk Utility to repair the computer’s internal startup volume.
Restart the computer and verify that it completes the startup process. If the computer still doesn’t start up completely, select the Install macOS option in macOS Recovery to update or reinstall macOS.
If the computer can’t start up to macOS and can’t start up to macOS Recovery, an icon with an exclamation point inside a circle appears. If you see this icon when attempting to start up the computer, follow the recommended steps in If your Mac starts up to an exclamation point in a circle.
Run the Mac Resource Inspector (MRI) diagnostic suite if possible.
Note: This test will gather diagnostic information and verify that thermal sensor readings are within limits. Check MRI results for any power, fan, or thermal warnings or failures.
Open and inspect the computer
If the issue wasn’t resolved or isolated by following support articles or running diagnostics tests, refer to the computer's repair manual to open and inspect the computer. A damaged or out-of-place part may be causing one of the issues.
Follow repair manual procedures to open the computer.
Inspect internal components and the enclosure for indications of physical or liquid damage, contamination, or burned or darkened areas.
Inspect the area around the heat sink and each fan for accumulated dust or debris. Use an ESD-safe vacuum or compressed air to carefully remove dust and debris from the heat sink and fans. Ensure that each fan spins freely and is not obstructed.
Note: This section requires ordering parts and tools. Replacing a part may not resolve the device’s issue. You can find other service options at support.apple.com/repair.
Replace the part
If the issue wasn’t resolved or isolated by following the previous steps, replace the logic board.
Note: This section requires ordering parts and tools. Replacing a part may not resolve the device’s issue. You can find other service options at support.apple.com/repair.
Troubleshooting no power
Identify issues
Read these articles if you notice any of the following issues:
The computer doesn’t turn on when you press the power button
The built-in display doesn't show any images
The DC power adapter connector doesn't seat into the iMac's power inlet receptacle properly or has an intermittent connection
If your Mac doesn't start up all the way
If your Mac starts up to an exclamation point in a circle
If your Mac starts up to Options with a gear icon
If you can't start up from macOS Recovery
Use macOS Recovery on a Mac with Apple silicon
If the issue wasn’t resolved by following a support article, continue to the next section.
Try quick troubleshooting steps
Inspect the computer for liquid damage. Contact with liquid can short internal circuits and cause fans to stop working.
Ensure that the computer is turned off. If you aren’t sure whether the computer is on or off, press and hold the power button to turn off the computer. Wait a few seconds, then press the power button again to turn the computer back on.
On the power adapter, inspect the DC connector for dust, debris, damage, or bent pins. Use compressed air to remove debris.
Check the DC connector on the power adapter for damage or debris, and corrosion on the DC connector pins. If you find corrosion, use a soft cloth to wipe it away, which may resolve the issue.
Note: A damaged connector has corrosion that can’t be wiped away.
Inspect the DC inlet connector and enclosure opening on the computer for signs of damage or debris.
Important: Do not use metal objects to clear debris or obstructions.
Note: The plastic guides inside the connector should be intact and not damaged or broken off.
Connect the power adapter to the computer with its DC connector. When you insert the connector, it may rotate slightly to align with the receptacle as the magnets seat the connector. When you remove the connector from the computer, always pull the connector straight out. Do not turn or twist the connector while removing it.
Use a different external iMac power adapter to verify whether the adapter being used with the computer is functional.
Run manual tests
If the issue wasn’t resolved by following a support article or checking for potential causes, run these manual tests to help isolate the cause of the issue:
Determine whether the computer has power by confirming any of the following:
The built-in display functions
A fan spins
A connected external display functions
If the computer shows any indications of power, refer to troubleshooting startup issues.
Open and inspect the computer
If the issue wasn’t resolved or isolated by following support articles or running diagnostics tests, refer to the computer's repair manual to open and inspect the computer. A damaged or out-of-place part may be causing one of the issues.
Follow repair manual procedures to open the computer.
Inspect internal components and the enclosure for indications of physical or liquid damage, contamination, or burned or darkened areas.
Inspect the area around the heat sink and each fan for accumulated dust or debris. Use an ESD-safe vacuum or compressed air to carefully remove dust and debris from the heat sink and fans. Ensure that each fan spins freely and is not obstructed.
Measure the voltage of the coin cell batteries on the battery board or logic board (depending on the model). If a battery is lower than 2.7 volts, replace the battery.
Note: This section requires ordering parts and tools. Replacing a part may not resolve the device’s issue. You can find other service options at support.apple.com/repair.
Replace the part
If the issue wasn’t resolved or isolated by following the previous steps, replace the following parts one at a time in the order shown. After you replace the first part, repeat the troubleshooting steps to determine whether replacing a part resolves the issue. If it still isn’t resolved, replace the next part.
If the issue is isolated to the power adapter, replace the external iMac power adapter or external iMac power adapter with Ethernet (depending on the model being replaced).
Replace the coin cell batteries on the battery board or logic board (depending on model).
Replace the logic board.
Note: This section requires ordering parts and tools. Replacing a part may not resolve the device’s issue. You can find other service options at support.apple.com/repair.