iMac 24-inch M1: Display Failure with Dark Band and Overheating

iMac 24-inch with M1: Display Failure with Localised Overheating – What Affected Users Need to Know Now

The owner of an iMac 24-inch with M1 (built 2022, 8 GB unified memory, 512 GB SSD) reported another display failure in August 2026: a wide dark horizontal band across the screen, accompanied by a clearly noticeable, locally confined build-up of heat – and this on a display that had already been replaced back in 2023. The user has since shut the machine down. No data loss has been reported, but access to the internally stored data has become difficult.

This article puts the case into context: what is known, what remains pure speculation, how you can safely check whether your device is affected – and above all, which well-meant actions can cost you your data permanently.

What happened?

The basis is a user report from the Apple Support Community (thread 256340157), which was indexed in August 2026. A direct request for the thread returned an Apple error page on 15 August 2026; the thread title and key details are confirmed via search indexing. The information must therefore be classified as a user report, not as a manufacturer's diagnosis.

The facts as described:

• Device: iMac (24-inch, M1, 2021) – according to the user from 2022, M1 chip, 8 GB shared memory, 512 GB SSD.
• The built-in display had already been replaced once in 2023.
• In August 2026, the replacement display again shows a wide dark horizontal band.
• A distinct, locally confined build-up of heat occurs at the display. The owner therefore switched the iMac off.
• According to the affected user, screenshots look normal, and a connected external LG monitor also shows a normal picture.

This observation – internal image disturbed, screenshot and external output inconspicuous – fits a fault in the internal display path (panel, its control circuitry or the internal connections) rather than a global rendering error. However, a fault at logic board level cannot be entirely ruled out, because not all image output paths are identical. This is a narrowing down, not a diagnosis.

Is this an isolated case?

The fault pattern is not new. On 5 August 2023, iFixit documented a comparable case involving horizontal lines on a 24-inch M1 iMac. MacRumors reported on 1 October 2024 about complaints regarding suddenly appearing horizontal lines that persisted after restarts. Tom's Hardware picked up the topic on 6 October 2024 and referred to a community thread that was 17 pages long at the time. Heise reported on 8 January 2026 about roughly 1,290 replies across two Apple Community threads (470 plus 820) as well as about a user campaign.

Important for context: forum posts are not a verified count of affected devices. There is no evidence anywhere of a failure rate.

„it is unclear how many customers are affected in total, or what the underlying cause of the problem is." – Joe Rossignol, MacRumors, 01.10.2024

„we must remember that even tens or a few hundred users complaining about this issue account for a very small percentage of iMacs sold." – Jowi Morales, Tom's Hardware, 06.10.2024

The theory circulating in forums and the media of an overheating high-voltage flex cable has not been confirmed by an Apple root cause analysis, measurement reports or a recall. It must not be treated as a diagnosis for any individual device.

Who and which devices are affected?

In this specific case: one reported owner, one device. The model basis is the iMac (24-inch, M1, 2021) – introduced by Apple on 20 April 2021 with M1 chip and a 24-inch 4.5K Retina display. 8 GB of memory and a 512 GB SSD were available configuration options.

Technically, Apple documents separate assemblies for this model: the built-in display, the camera and embedded DisplayPort flex cable (eDP – the internal data line to the screen) as well as the display backlight flex cable for the backlighting. The iMac additionally supports an external display up to 6K at 60 Hz – which is why a normal picture on the LG monitor is not a contradiction to the failure of the internal panel.

Symptoms you can recognise it by

• A wide dark horizontal band or persistent horizontal lines on the built-in 24-inch display.
• The lines remain even after a restart.
• Clearly perceptible, locally confined heat at the display – in comparable reports frequently in the upper right area.
• Screenshots and the image on an external monitor remain normal.
• Comparable reports mention occurrence after roughly 18 to 24 months – without any proven common cause.

How to check whether you are affected – without making anything worse

1. Safety first. If there is currently, or was shortly before, distinct localised heat, a burning smell, smoke, discolouration or crackling noises: stop testing. Switch off, disconnect from power, let it cool down. No repeated start-up attempts for troubleshooting purposes.
2. Document while the device is switched off. Photos of the band, photos of the conspicuous area after it has safely cooled down, serial number, purchase and repair receipts – in particular proof of an earlier display replacement. This secures your evidence and speeds up service intake.
3. Only if the device is thermally inconspicuous: check once whether the band is already visible at start-up and whether a known-good external monitor shows a normal picture. If heat develops, switch off again immediately. This observation is not a determination of the cause.
4. Apple Diagnostics – likewise only if the temperature is inconspicuous. On Apple silicon Macs: switch off, hold down the power button until the start-up options appear, then hold down Command-D. From macOS Tahoe 26 onwards, a display diagnostic may be selectable. Note down the reference codes.
5. Clarify your backup status. Check whether a current Time Machine backup or another backup on a different medium already exists. If the data status is unclear, do not carry out any deletion, formatting or reinstallation steps.

Apple itself puts it this way regarding diagnostics: „If you think your Mac may have a hardware issue, you can use Apple Diagnostics to help determine which hardware component might be at fault." (Apple Support). An inconspicuous diagnostic result, however, is no clearance for continued use – in the case of localised overheating, software is no substitute for a visual and safety inspection by a qualified repair specialist.

What you should do now

1. Leave the iMac switched off and disconnect the power cable if the localised heat build-up was pronounced or recurs. Do not try to "reproduce" it with maximum brightness, benchmarks or long run times.
2. Do not open anything. The display is glued in place. Apple requires special tools for this and warns explicitly: „Caution: Don't strain the flex cables that are connected to the logic board and back of the display." (Apple repair manual).
3. Arrange a professional inspection – with a qualified repair specialist experienced with Apple silicon iMacs. Provide the complete picture: fault pattern, normal external output and screenshots, localised heat, previous display repair. Ask for a separate examination of the display assembly, the eDP and backlight connections, the power supply, the temperature sensors/fans and the logic board – instead of a blanket complete display replacement.
4. State your data priority in writing. Before a parts replacement, any logic board work or a reset, have it clarified whether your data is still needed and how gentle access can be achieved.
5. Only back up after safety clearance. Only once a specialist has ruled out the thermal risk after inspection and the Mac runs stably should you back up data to an external drive. Without that clearance, do not force a long backup session.
6. Hand over your documentation: Diagnostics reference codes, photos, repair receipts. In the event of smoke, a burning smell or further rising heat, do not continue operating the device but agree on a safe procedure beforehand.

If you are realising right now that your last backup was far too long ago: the Backup Assistant helps with the question of which backup concept suits your device – before the next failure hits.

What you must never do

This section is the most important one. As far as is known, the data on the iMac's 512 GB SSD is currently intact. That is precisely why it is being decided right now whether it stays that way.

• Never run "Erase Mac", "Delete Volume Group" or a format – neither in macOS Recovery nor in Disk Utility. Apple explicitly describes erasing an Apple silicon Mac as permanently deleting your files. This is the single most confirmed destructive step of all.
• Do not start a macOS reinstallation if it involves erasing the internal startup volume group. The problem is not the installation itself, but the erase step preceding it – it removes your local files for good.
• Do not install recovery software on the internal SSD and do not write any recovered data back to the same medium. With this fault pattern it is not indicated anyway – it merely creates additional write operations on the one affected medium. Recovered data always belongs on a different drive.
• No "heat testing". Do not switch the device on repeatedly, do not run it under load for long periods, do not turn up the brightness to test it. Whether this directly destroys data is not proven – but it can certainly aggravate thermal and electrical consequential damage.
• No opening, lifting, reseating or manipulating of the display and internal flex cables by yourself, and certainly not while powered. The glued display and the delicate flex connections are exactly the places where additional damage occurs – and with it the loss of clean fault documentation for the service provider.

In practice, it is almost never the original defect that costs data for good. It is the well-meant attempts that follow: the quick reset, the "let's just set it up fresh" idea, the recovery tool on the same drive, the tenth start-up attempt on a hot device. None of these steps can be undone afterwards.

Is there a fix, an update or a replacement programme?

As of 15 August 2026: No. There is no Apple recall, no publicly listed replacement or repair extension programme and no Apple-confirmed software update for horizontal lines or localised display overheating on the iMac (24-inch, M1, 2021). The public Apple page listing service programmes names no corresponding iMac programme.

Apple provides repair manuals, Apple Diagnostics and regular service channels for the model. Comparable reports describe case-by-case decisions on repair costs and goodwill – no entitlement and no general remedy can be derived from that.

Why this case belongs in professional hands – and how RESQ specifically helps

The damage pattern of "dark band plus localised heat" seems clear-cut – but it is not. That is exactly where the trap lies. Panel, internal eDP data connection, backlight flex cable, power supply, thermal management and logic board cannot be reliably distinguished from one another without a professional examination. A blanket complete display replacement may therefore miss the actual cause – in the case described, the failure recurred in August 2026 after a display replacement in 2023.

What a specialist workshop does differently from any attempt at the kitchen table:

• Separate diagnosis instead of a suspected diagnosis. Display assembly, internal connection cables, power and thermal path as well as logic board are examined individually – before any component is replaced.
• Safe opening of a glued display. The 24-inch iMac cannot be opened without damage without suitable tools. This is precisely where DIY attempts cause the consequential damage to the flex cables that Apple itself warns about.
• Assessment of the thermal risk. Whether a device with conspicuous localised heat may run stably long enough at all to back up data is a professional decision – not one that should be made by trial and error.
• Data before repair. If data has priority, the backup is planned before any intervention and not handled on the side. Where necessary, work is done on a copy, not on the original.

The process at RESQ is deliberately designed without any upfront commitment from the customer: you describe the case, we carry out a free initial assessment and tell you honestly what can be deduced from the described picture – and what cannot. A cost estimate follows. Only then do you decide whether we go ahead. A successful data recovery can never seriously be promised in advance; every case is assessed individually.

The direct route: request a free initial assessment and cost estimate. If you would like to read up on the process and services in advance, you will find them at Data recovery at RESQ. If your sole focus is the device defect because the data has already been backed up, Repair at RESQ is the right starting point. If you would like to commission the case directly, you can also create an order in your customer account straight away.

Conclusion: switch off, document, have it examined

An iMac 24-inch with M1 and a display failure accompanied by localised overheating is first and foremost a functional failure – not a confirmed data loss. The fact that screenshots and an external monitor remain normal suggests that a data backup before a display repair may still be possible. That is a good starting position, but it says nothing about the condition of the SSD or the logic board.

As of 15 August 2026 there is no official replacement programme, and no confirmed common cause either. What you can do yourself is limited and, for exactly that reason, clear: device off, power cable out, photograph the condition, collect receipts – and delete nothing, format nothing, open nothing.

Everything else belongs in professional hands. Have the fault pattern examined before another complete display replacement is commissioned and before your data is put at risk by a careless step: get your case assessed for free now.