Persistent horizontal lines appear on iMac screen

My advice is to turn off the LCD lighting on your iMac (set it to 1).

By reducing the brightness you'll be able to see that the temperature at the top of the LCD becomes normal and the worry about over-temperature will disappear.

Then buy a new external monitor.

There are very good monitors available relatively cheaply.

I worked like this for almost a year when my iMac was broken and without any problems.

It's the same as having a (very expensive) Mac mini...

But at least you can keep working until Apple sort it out.

UPDATE

I faced an overheating issue in the top right corner of my 2021 M1 iMac 24”, which eventually led to display failure with burn marks and a smoke smell after 2.5 years of usage. Initially, Apple India denied free repair as the device was out of warranty and offered only paid service. I escalated the case to Apple USA with proof that this was a known horizontal lines issue (widely reported in forums and media) and highlighted the severe safety threat to my family. After sharing high-resolution photos, videos, and diagnosis reports, and insisting on escalation to their engineering team, Apple granted me a one-time exception (CS Code) for a free display replacement. 🙏 After 90 days of usage with the new display, it is working completely fine, and I sincerely thank Apple for their credibility and for standing by their customers in critical situations.

For post-warranty issues, there’s AppleCare Products - Mac - Apple. Too bad you didn’t sign up. Nonetheless, use Feedback - iMac - Apple to vent. But before doing so, schedule in-store Apple Repair for a free diagnosis and repair estimate.

All the best.

zardoz73 wrote:

Apple, fix this. When people bring these 2021 M1 iMacs into the store, fix them for free. It's really lame to get just two years out of this computer, when it clearly can go for several more.

Remember, Apple isn't here. They probably won't see your request, and if they do, they won't respond to you here. This is a user-to-user forum.

I am sure somebody must have provided a feedback link. If not: Product Feedback - Apple

If the problem is listed here on the link below yes. If not, it is out of warranty by now and you will pay the cost for repair. Unless you have AppleCare coverage then its covered.

Apple Service Programs - Apple Support

Hi everyone,

I’m also experiencing black horizontal lines on my iMac M1’s display. This issue affects my work and overall user experience.

If you’re experiencing black horizontal lines or other display issues on your iMac M1, I encourage you to send feedback directly to Apple. Sharing your experiences can help bring attention to this issue and may lead to a solution.

You can submit your feedback here: Feedback - iMac - Apple

It’s important for us as a community to let Apple know about recurring problems so they can address them effectively.

I understand that Apple is aware of this issue.

Based on my personal experience, I would offer the following advice:

Recommendations:

1. Exercise patience—this process may require significant time and persistence.
2. Maintain a professional and polite demeanor when interacting with Apple customer support.
3. Clearly articulate your situation and respond positively and cooperatively to all requests, even if they seem numerous or personal.

Important Considerations:

1. Requests for detailed information or additional steps indicate that the support team is actively working to resolve the issue. A professional, friendly, and cooperative approach on your part will help foster a productive interaction.
2. The individual handling your case has a responsibility to collect comprehensive details to address the matter effectively. This may include intrusive or personal questions and, in some cases, granting limited remote access to your iMac.
3. While some requests may seem inconvenient, they are part of a professional troubleshooting process expected from Apple.

After completing these steps, you may need to wait. If follow-ups are necessary, do so politely and emphasize that the problem appears to be a hardware issue affecting certain units of this model — an issue that should not occur under normal circumstances. Express confidence in a fair resolution and a willingness to collaborate towards a solution.

Finally, based on Apple’s history of addressing similar unexpected issues, I believe it is likely that they will introduce a support program for this specific problem in the coming year. Until then, I recommend maintaining patience, faith, and optimism.

Hi @Universall

It seems you’ve encountered the same issue with floating lines as many of us. However, in your case, there appears to be an additional defect.

The dark spot in the top-right corner of your monitor indicates a separation between the LCD screen and the protective glass. Since these layers are glued together, the separation likely caused the LCD to crack, leaving the affected pixels permanently black.

This could have resulted from one of two possibilities:

1. A deliberate attempt to separate the LCD from the glass—perhaps to access the internal circuitry, such as the side cables.
2. A significant temperature increase that caused the adhesive to weaken, leading to the separation and subsequent damage.

In my opinion, it’s more likely that the damage occurred inadvertently, possibly during a prior inspection. When you asked the technicians to assess the fault, they may have attempted to separate the LCD from the glass, unintentionally causing the breakage.

To address this, I recommend being persistent and extremely polite when dealing with Apple’s support team. Always request to escalate your case to a supervisor, as standard employees may not have the authority to take your complaint to the necessary level.

Patience, thoroughness, friendliness, and good manners will be crucial in resolving this matter. This issue affects not just you but also Apple, whose reputation is at stake due to this widespread failure.

Best of luck!

[Edited by Moderator]

Same. Gently used M1, purchased 2021. I'm in Hawaii, curious how many are posting from a tropical environment? Lines appear diagonal in photo, but they are horizontal.

I have the same problem with my iMac M1 (2 USB-C ports) bought in Singapore in September 2021 (model number ending with ZP/A - Southeast Asia). The problem appeared yesterday.

So the symptoms are the same: iMac M1, 2 years in use, mostly Asia manufactured models affected.

Same problem here. Mine started all of a sudden 10 days ago when those horizontal lines appeared on my screen. The weird part is when they first appeared it also had a cluster of red and black pixels top right.

After restarting and shutting it down several times it did nothing. Only after leaving it without being connected to the power cable for more than two days the cluster disappeared. But the lines are still there.

Isso é um absurdo. A Apple precisa fazer um recall urgente.

I am having the same issue since last week.

Before this happened, I noticed that the right side of the monitor was hot and the fan started.

Bought my iMac in April 2022.

I am also facing this problem with my 2021 M1 IMac. I bought it in Brazil around 2 years ago.

This happene to me today unfortunately. While typing in Notes app, the lines suddenly appeared and the area where this lines appear appears to be very hot.