Horizontal lines appear on iMac 2021 24'' screen

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bil1912 Author

Level 1

5 points

Horizontal lines appear on iMac 2021 24'' screen

Problem Description:

Persistent horizontal lines appear on the lower part of the screen and sometimes screen light turn off. Then screen resume again by restart.
This problem arises without any physical damage.

Steps Taken:

Connected to an external display: The external display works fine even when screen light go off, indicating the issue is with the iMac's internal display.
Reinstalled the OS: The problem persisted post reinstallation.
Avoided operating the iMac for a week: No change in the situation.

Concerns:

The cost of screen replacement is high, and there's no assurance that it will resolve the issue permanently.

[Edited by Moderator]

iMac 24″

Posted on Aug 3, 2025 9:41 AM

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Answer 1

Top-ranking reply

steve626

Level 6

13,551 points

Aug 3, 2025 9:46 AM in response to bil1912

That's a sign of hardware failure (or impending failure). Others have reported similar symptoms in Apple Discussions. It is very uncommon to see this but apparently it is something that other users are also reporting. You have properly narrowed the failure down to the internal screen assembly. For that, there is no user process to fix, it has to be replaced by an Apple authorized service center. If you have AppleCare+ this repair will be covered. If you do not have it, see if you can add it. You are correct that the problem could return after repair, but there really is not any other option, other than use of an external monitor instead of the built in one.

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Answer 2

Old Toad

Level 10

215,088 points

Aug 4, 2025 10:49 AM in response to bil1912

You're experiencing a hardware failure which Apple hasn't recognized as a manufacturing defect. If and when Apple offers a "recall" on the M1's screens keep you eye on Apple Service Programs - Apple Support website. Reports have listed the repairs from $600 US to nearly $1000 US.

If the iMac with an external monitor becomes too clumsy and cluttered to use you might consider getting a Mac Mini M4. A 10 Core Mac Mini M4 with 16 GB RAM and 1 TB SSD ($999 + tax) which is considerably less than a similarly configured new 24" iMac ($1799 + tax re 07/2025) since you already have the monitor.

If there is a "recall" on the M1s it will be posted there.

Right now you've already on the road to "recovery" with the external monitor.

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