Persistent horizontal lines appear on iMac screen

Jotap62 wrote:

Dear Old Toad,

According to Apple support, it's an LCD malfunction and the only solution is to replace it.

So it's not a software problem.

It's a hardware problem.

That's already established.

Then maybe the most economical path forward might be an external 3rd party monitor. When you upgrade to a new Mac it can be a second monitor for that Mac.

Some claim "  Tim Cook's official Apple email (tcook@apple.com). Cook almost never responds directly but Apple, like most large corporations, has an executive response team that monitors his email inbox and manages and escalates customer complaints. Include the information you've found about this being a widely reported defect. Mention your long history as an Apple customer and how this experience has shaken your faith in product quality. A member of the executive response team will most likely respond, and they could well wind up authorizing the repair at no charge.

PS: For me even repair at no Charge don't feel fix this Line problem partly is All due to " Design flaws how and why they do back the same again " This line issue first surface from M1 iMac , now even M3 iMac which I using it also has this problem...

There might be a connection between auto-adjustment of brightness and the onset of flickering. My iMac first had the flickering one week ago. I turned it off and on. The flickering disappeared, but a black line persists. Since then, the flickering appeared a few times more. It seemed start when there's a change in environment light. For instance, I pulled down the curtain. My room became darker. The brightness of the display changed (I had auto-adjustment of brightness on). Also appeared flickering. I then disabled auto-adjustment of brightness. Flickering hasn't re-appeared since. Just to share my observation, in case it might be useful.

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.

I purchased four 2021 M1 24" iMacs for my office in Taiwan, across different months in late 2021. All of them have been well cared for, yet each began developing the same screen issue one after another starting in March this year. At this point, 100% of my units are affected.

From reading various threads and forums, it appears Apple has occasionally offered one-off free repairs to users who know how to push for them. For example, a petition requesting a Service Program quickly led to Apple granting free repair to the petition's initiator.

The iMac line is positioned as a premium product in the personal computer market. My previous iMac lasted over seven years without issue, and many older Intel-based models still run flawlessly today. Selling a product with such widespread defects undermines that reputation. Until Apple properly addresses this issue, I will be cautious about purchasing new Apple products.

I from SG, same replay from other SG iMac users.

what I have research

​Even tech repair iMac do mention this 

" Known iMac 24″ (M1 2021) Screen Line Defect: Recently, a flood of user reports has surfaced about horizontal lines permanently appearing on the 24-inch M1 iMac’s display after ~2 years of use. Apple hasn’t officially recalled this, but evidence suggests a hardware design flaw. Technicians discovered that a flex cable in the display carries high voltage (around 50V at full brightness) and tends to overheat and burn out over time, causing short-circuits that produce black horizontal lines. Unfortunately, the only reliable fix for this issue is to replace the entire display assembly, because the cable is bonded to the screen. Apple Support has generally told affected users that an LCD replacement is the solution. However, replacing the screen is costly (often on the order of US $600–$700 for the 24″ iMac), and if the underlying design hasn’t changed, the problem could recur in a couple of years. "

PS: I NEVER use Full brightness. I always set Auto brightness. According from the tech , EVEN you get fix the problem Could Recur in a couple years....

Check out my replay. Tech do mention " Design flaws " on M series iMac. I Never know M series got what Lines suddenly appear issues after using one year or so. Just Happen this weekend I use my M3 iMac as usual. Wake up the iMac and suddenly notice there are lines appear on the bottom of my iMac.

I do owned other old iMac , all at least the screen is Ok one is bought in 2015. The screen will turn to pinkish hub and will have burn mark easily but that is OK , after a while it will gone and since already use More than Two years till now. But Cannot accept is this M series iMac , next I own M3 iMac only bought in 2024 and haven't reach two years Suddenly lines appear.... Now I worry is the lines will spread to the entire screen literally you can't view. Even the lines now appear on the bottom of my iMac screen I already feel..... A lot already bring their iMac go Apple store bring up this case of M series flaws but Same old reply , Have to pay get it Fix.

Only some like managed to get fix Free but thought lots of hassle feedback here and there. Next Even it get fix, the Problem will come out. Which the tech mention.

Here is what It mention " " Known iMac 24″ (M1 2021) Screen Line Defect: Recently, a flood of user reports has surfaced about horizontal lines permanently appearing on the 24-inch M1 iMac’s display after ~2 years of use. Apple hasn’t officially recalled this, but evidence suggests a hardware design flaw. Technicians discovered that a flex cable in the display carries high voltage (around 50V at full brightness) and tends to overheat and burn out over time, causing short-circuits that produce black horizontal lines. Unfortunately, the only reliable fix for this issue is to replace the entire display assembly, because the cable is bonded to the screen. Apple Support has generally told affected users that an LCD replacement is the solution. However, replacing the screen is costly (often on the order of US $600–$700 for the 24″ iMac), and if the underlying design hasn’t changed, the problem could recur in a couple of years. "

My local Apple dealer was charging me $900 in order to repair the screen, I ended up buying a new display at Amazon and replacing it by myself, it cost me around $350, is not hard but you have to be careful because there are some connectors that can be break if you rip them hard... Display is now working 100% fine ( for now ) .... Thank you Apple for nothing!

What i'm thinking is that Apple is well aware of this problem, but they will not recognize it because it will cost them TONS of money, also because this is a design problem, it will affect eventually other models that share the same design, M2, M3, etc, etc.. not just M1 and this will carry a huge lost for this product, there is no other reason why they are not assuming their responsability.

I've posted once before in this topic and I'll repeat it again:

You have 3 options:

1 - pay the ~$600 US price for  Apple or an Apple Authorized Service Provider to repair the monitor (which is over ½ of a new M1 Mac Mini).

2 - get a monitor and use it with your M1 iMac. You can get a 27" or 32" monitor from $140 US on up.

3 - get a new Mac. If considering this option consider the following: a 10 Core Mac Mini M4 with 16 GB RAM and 1 TB SSD ($1084 US) with a 32" LG 4k monitor ($331 US) from Amazon.com)  is $1415 which is $541 less than a similarly configured new 24" iMac ($1956 US)  re 07/2025. Keep your keyboard and mouse from your current Mac for use with the Mini. 

I got the above Mini with a 32" LG 4K monitor w/speakers for only $60 more than the 27" (didn't know the Mini had a speaker).  There are many monitors available in 27" size on up for $100 US to $500 US depending on what features you want.  The monitor prices are before tariffs.

Just some food for thought.

ADDENDUM: in addition to the 3 choices above keep tabs on the Apple Service (Recall) Programs - Apple Support

Let us all report and complain this to Apple --> Feedback - iMac - Apple

I had the exact same issue as everyone here. The first few nights (2 or 3), I used multiple pixel refresher videos from YouTube (5 hours or so each time), at max brightness. Then I continue to use the computer normally but on a second screen. Keeping the iMac screen at the lowest brightness for over a week.

Also, I pray a whole bunch :)

Unfortunately my iMac 24" M1 purchased at Apple Store on 9 August 2021 suddenly developed same screen issue (half screen KO and continuous huge flickering).

Erasing HD and installing Sonoma fresh copy didn't fix.

Contacted Apple Italy they told me that as it is out of warranty payment for repair is up to me.

This is obvious, but as I'm not the only one suffering this fault and IMHO it's a building defect I hoped Apple would have had a special attention to my case, but no hope.

I had to purchase a new Mac Mini M4 and my loved iMac 24 is on its way for rubbish, 1700 euros lost.

Never more an iMac !

Really disapponiting

Giorgio

I, like many others apparently, have the same issue with lines appearing on the screen. I took it in for diagnosis and it was determined that the problem was hardware related. The remedy is to replace the screen for a cost of about $700. I will probably buy a non-Apple monitor to hook up externally at a cost fair less than the repair.

Just stumbled upon this thread. It happened to me today.

I can’t believe the similarities too - approx 2 years of use, abrupt development of vertical lines, scorching heat on top corner of the screen.

I called Apple support and asked if this was a common occurrence, and was told that they have gotten calls about it.

I think it would raise awareness around the issue if we called to report en masse.

800 186 1087 (toll-free, if anyone needs it).

Dear Old Toad,

According to Apple support, it's an LCD malfunction and the only solution is to replace it.

So it's not a software problem.

It's a hardware problem.

That's already established.

So to everyone who has this problem, there's no point in wasting time trying to find out which App is causing it or which OS update is to blame and reinstalling the OS and all the Apps again and risking losing data trying to solve a problem that has already been determined to be a hardware issue.