How to diagnose the 5 most common hardware failures on a MacBook/iMac?

The Apple ecosystem is renowned for its reliability and elegant design .

However, even the most robust machines, such as MacBooks or iMacs , are not immune to hardware failures. A Mac that refuses to turn on, slows down inexplicably, or displays graphical artifacts can turn a productive day into a real frustration.

Faced with these symptoms, panic is often the first reaction. However, a methodical approach to diagnosis can save you valuable time and potentially spare you a costly repair.

In this article, I guide you step by step to diagnose the 5 most common hardware failures on a MacBook or iMac, give you troubleshooting or confirmation tips, and tell you when to call a Mac repair .

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Why perform a hardware diagnosis before repairs?

Before replacing expensive parts, it is crucial to confirm that there is indeed a material defect, and to properly identify which one.

Apple notably offers an integrated tool, Apple Diagnostics , to test several internal components (memory, graphics card, fans, etc.).

In many cases, the symptoms are distinct enough to point to the correct component (hard drive, power supply , screen, etc.). This avoids unnecessary replacements, extra costs, and saves valuable time.

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The 5 most common hardware failures — and how to diagnose them

Here are the five types of hardware failures commonly encountered on MacBook and iMac — with their typical symptoms, simple tests, and what to do next.

Good to know: If the symptoms persist despite your efforts, or if the component to be replaced is integrated or inaccessible, it's time to contact a specialist repair shop. For Mac repairs , you can visit madmac-informatique.fr for a more in-depth diagnosis or replacement of faulty components.

1. power supply /charging problem (battery, adapter, charging circuit)

Typical symptoms

• The Mac either won't turn on, or shuts down immediately despite the adapter being plugged in
• The MacBook briefly displays "Charging" and then nothing else
• The indicator light on the adapter (MagSafe or USB-C) does not light up
• The battery discharges very quickly, even with little use.

Tests and diagnostics

1. Check the adapter and cable: test another adapter or cable to rule out an external fault.
2. Inspect the connectors (MagSafe or USB-C): dirt, oxidation or a damaged pin can block charging.
3. Remove all external devices (disks, hubs, etc.) and restart.
4. Use Apple Diagnostics to see if a charging error code appears.
5. Check the battery status in "About This Mac" → "System Report" → " Power Supply ".

What to do next

• If the adapter or cable is the problem, replace it.
• If the battery is defective (severely reduced capacity, swelling…), it will need to be replaced.
• If the internal charging circuit or the motherboard is faulty, this will require professional intervention.

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2. Disk or storage failure (SSD / disk)

Typical symptoms

• Very slow Mac, extremely long disk access times
• File system error messages, “corrupted volume”
• Grey screen, crash on startup, stuck on the loading screen
• Mechanical noises (on models equipped with HDDs)

Tests and diagnostics

1. Launch Disk Utility to check/repair the disk (recovery mode or with an external drive).
2. In Apple Diagnostics, a storage-related error code may appear.
3. Run the command diskutil verifyVolume / in Terminal (recovery mode).
4. Use third-party tools like EtreCheck to detect signs of corruption or a failing SSD.

What to do next

• If the disk repair tool finds moderate errors, correct them and back up immediately.
• If the disk is physically damaged or the SSD has dead blocks, replace it.
• Restore your system after replacing the disk, and check for backups.

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3. Problem with RAM or faulty memory modules

Typical symptoms

• Random crashes, kernel panics
• Application crashes, spontaneous restarts
• Mac restarts unexpectedly during demanding tasks (video editing, gaming, calculations)
• Extreme slowness in certain operations

Tests and diagnostics

1. Run Apple Diagnostics — a memory error code may be reported.
2. If your Mac allows you to remove the RAM modules (some older iMac or MacBook Pro models), test each stick individually.
3. Observe the system logs (via Console) for errors of the type "memory error".
4. If the Mac has the option, use a benchmark/stress test tool (memtest) from an external drive.

What to do next

• Replace the faulty memory module.
• If the RAM is soldered or inaccessible (as is the case with some recent models), a specialist service will be required.
• Make sure you buy RAM that is compatible with your model.

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4. Graphics card/GPU or video chip failure

Typical symptoms

• Visual artifacts, strange lines on the screen
• Black screen after startup (but the Mac seems to be starting up — you hear sounds)
• Restarts during heavy graphical activity
• iMacs with dedicated graphics cards: crashes, blemishes, or flickering

Tests and diagnostics

1. Run Apple Diagnostics: codes like VFD001 to VFD004 indicate display/GPU errors
2. Test the external display: connect an external monitor to see if the problem persists.
3. Start in safe mode or under a lighter OS to isolate the fault.
4. Look for crashes in the logs (Console) indicating GPU, driver, or kernel panic.

What to do next

• If the graphics card is a separate removable one (on some older iMacs), replace it.
• If the GPU is integrated or soldered to the motherboard (as on many modern Macs), it is a more delicate repair — often replacement of the motherboard or GPU block — that a specialized workshop will have to handle.
• Back up your data immediately if any serious signs appear.

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5. Problem with the screen / panel / display logic board

Typical symptoms

• The screen remains black or displays a white screen, even if the Mac is turned on
• The image is partial, distorted, or displays with lines (flickering)
• The screen works temporarily, then shuts off
• On MacBook: cracks, dead pixels, or missing backlight

Tests and diagnostics

1. Connect an external monitor: if the external display is correct, the problem is with the screen or the cable.
2. Launch Apple Diagnostics to detect a display or HDR defect.
3. Check the internal connectors (video ribbon cable) if they are accessible (near the hinge).
4. In some cases, a simple recalibration or reset of the video controller (via SMC/PRAM) may help.

What to do next

• Replace the panel or the entire screen.
• If it's the video cable or the internal connector, replace them or reconnect them properly.
• If the display logic board is faulty, this may require a motherboard or GPU component replacement.

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Good diagnostic practices and recommendations

Use Apple's built-in tools

• Apple Diagnostics / Apple Hardware Test : This is the first tool to use to isolate faulty components.
• Safe Boot or recovery mode allows you to test your Mac outside of the user environment.
• Disk Utility , Terminal (diskutil) , Console : invaluable for detecting disk, memory, or kernel log errors.

Save your data before any manipulation

Before opening your Mac or replacing any components, make sure you have a complete backup (Time Machine, clone, external drive). This will prevent data loss in case of an error.

Proceed by elimination

Test one component at a time (RAM, adapter, cable, disk, etc.) to narrow down the area of ​​investigation. Replace one part at a time and check if the symptom disappears.

Know the limitations of your model

Some recent Macs have soldered components (RAM, storage, GPU), which makes certain repairs impossible without replacing the entire motherboard. In this case, it's best to consult a professional.

Hire a professional Mac repair