Persistent horizontal lines appear on iMac screen

Hey guys,

I posted here a few months ago about my problem, same way as yours, on an iMac M1. Started in august, in December the situation worsened, and in February, beyond the lines, the screen started to get VERY hot. During this time, I contacted Apple several times to report what was happening, even though they refused to repair it. I took photos and videos and documented everything, talked about this discussion and other reports. The situation only changed when I reported that the screen was getting very hot and was passed to a senior support and after a few days took the display for evaluation. It took about six months, many contacts, persistence and patience, two in-person evaluations, and luck to be served by attentive people. But it worked out: in March, I was informed that they granted me an exception (they emphasized this point) and approved the replacement of the display free of charge. I don't know if it was luck, the way things work in Brazil and customer service, or some genuine concern for customers, but it worked out. Keep reporting. I don't know if the feedback really works, but maybe talking to people will. Good luck!

haixin512 wrote:

Keeping contact apple feedback with the info below: (i do it once a week now)

Product Feedback - Apple

+1 It is a good idea to keep sending feedback and to call.

The kicker here is, that Apple does not make the display panels. They out source the display panels from third-party suppliers like Samsung, LG and others.

As I recall, something similar happen to some displays panels in the late 2005 and early 2006 iMac's. After a couple of years, some of the display panels starting getting multiplying vertical lines. Sadly it took Apple another year to settle-up with the display manufacture and acquire enough replacement displays to start an Extended Service program.

my problem was the same as yours, except for the overheating location (mine was at the top of the display). only when I reported the overheating that almost burned my finger, their attention changed. after that, they transferred me to senior support. I took pictures of my finger (it was superficial, but it happened), showed the overheating area, made videos showing the heating location and how the lines flashed more intensely at these moments. It took some time and two in-person evaluations, but it worked. they made an exception, and i had the display repaired free of charge.

Hi, I just want to thank you all in this post, because you helped me save A LOT. I had the same issue with my iMac 24" (late 2021), as shown in image below, and after 2 attempts calling to Apple, I was gifted with the free replace of my screen. I'm in Brazil, and here, replacement parts are more expensive yet, so, it was awesome. What I did:

1) First attempt > After going to an Apple authorized service, and be notified that I just had one thing to do (replace the entire display), I called to Apple and had a long conversation with an assistant, and he said to me that Apple doesn't give free displays like that, and also asked me to report the authorized center who did this. From this call, they gave me a link where I could upload photos and videos of the malfunction. No response and nothing happened for a week.

2) Second attempt (1 week later) > I went to another Apple authorized partner to get a new quote. In this partner, the same thing > no repair, buy a new expensive display. I left my iMac to repair, and was about to shut up and pay. But, in this very day, I read this post again, went to the Apple chat and there they escalated me to a Senior representative, who called me and saw that I had already filed a complaint and that this was the second time I was trying. So, this incredible and very kind representative (Roberta), asked me to report the problem and send the most recent quote for the repair. Ater 40 minutes, she came back with good news and said that I was eligible for the free repair, and she reached the service provider to "make an exception" (her words) to repair my screen for free, and that this "exception" will happen only once.

So, my advice is that you try one more time. In my case, it worked! I hope you can have yours fixed as well. And that Apple check this issue, because it seems to be a repeated question with many users. I never had problems with my mac devices, this is the first one. Thanks a lot.

Have you blown the dust out of the intakes lately?

What temperatures does this App report? Especially the GPU.

This App can be used to speed up the fans, all my iMacs would be dead without it.

Never ever ever drop fan speeds below the speed that the Mac itself is calling for.

MacFansControl…

https://www.crystalidea.com/macs-fan-control

I can't remember which video i followed but pretty much all are the same, here is an example:

https://www.youtube.com/watch?v=uBjMr--idKo

There are several youtube videos that explain how to replace the imac M1 display that are pretty helpful... I remember that i just had to be very careful with the connections, some of them can break if you pull too hard, also take a look how they unhook so you do it the right way, the display I got included all the tools you need.

Some displays might not come with the camera (mine didn't) so you just have to remove it from the old display and place it back, be careful and take a good look how they are placed, some new glue could help, besides that, it's nothing complicated.

In order to get the display you can buy it form Am*zon or Eb@y, i got mine from Am*zon, one thing that happened after i updated the OS to Tahoe is that it recognized a new display so the computer performed a hardware check and that was it... iMac is working again.

One way you can prove or disprove that's its hardware or software is to erase the drive and install a new system. Do not migrate your user data to it for this test. If the problem appears then it's hardware and not 3rd party software issue.

If gone then it's software and you should manually restore the contents of your Music, Pictures, Documents and Desktop folders from your latest Time Machine backup to the new user account (which should be an admin account and can be your original user name and password.

Then you should reinstall all of your 3rd party software. NOTE: be sure to note all of the activation codes for those 3rd party apps that require them.

Also do not installed and run any "cleaning", "optimizing", "speed-up", anti-virus or VPN apps on your Mac on your new installation. A VPN is OK if it's required by your employer, bank or school.

If it's hardware related you'll have to make a decision as to how to address it. A possible alternative is to get an inexpensive 27 inch monitor and run it along with the damaged monitor and use it as your primary monitor.

Just some food for thought.

Addendum: all of this requires you to have a full and current backup of your boot drive with Time Machine or some other backup app.

If there ever is a fix it will be announced here: Apple Service Programs - Apple Support

So make a bookmark of that site and check it frequently. Also anyone who has this problem and has not taken it into an Apple Genius bar should so they know the extent of the problem.

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

What they didn't say was why this problem is occurring after two years of using the iMac on so many computers.

So, as Apple hasn't yet assumed that it's their fault, what I did, given the lack of concrete answers from Apple, was to take my iMac to a technician and ask him to assess the problem to see if it's a construction problem or just a random fault.

The explanation I was given was as follows:

In terms of circuitry, everything seems to be working properly.

The problem, apparently, lies in a cable that also powers the LCD, which is located on one of the tops of the screen, and which, in order to be replaced, requires detaching the screen glass from the LCD itself, which is a very sensitive operation and almost impossible to carry out without damaging the LCD.

So the only option is to replace the entire LCD (LCD+main boards+screen glass).

Also, according to the technician's explanation, this cable (of the FFC/FPC type or Flat Flexible Cable / Flexible Printed Circuit), it has to sustain a very high voltage (around 50V) to power the LCD (this despite the iMac's power supply being 15.9V), and it heats up a lot!

So, what happens after a while (in this case after about 2 years) is that it starts to burn out and degrade at the connector, to the point where it lets the signals leak between the various connectors and short-circuits some of them, which ends up causing those lines that we are all unfortunately familiar with.

The level of brightness makes a fundamental contribution to this problem. Thus, the higher the brightness used, the sooner the problem occurs.

This is easily understood by measuring the difference in temperature at the top of the screen when it is at its lowest brightness level, compared to when it is at its highest. It's quite a big difference!

When it's at its lowest brightness, it's practically room temperature; when it's at its highest, you can almost "fry an egg"!

I think that as soon as Apple recognizes that there is a problem with these computers, the first thing it will do is make a change to the OS that reduces the maximum brightness limit allowed (to less than 500 nits). Time will tell...

Why does this happen?

For at least one of three reasons:

1- a design flaw - so this problem is likely to occur in a large number of devices;

2- a defect in components - the problem is limited to a few cases;

3- use of components below Apple's standards - the problem may be limited, or more widespread.

This was the explanation I was given. I'm not a technician. Only Apple will know the exact reason(s).

If I had to guess, I'd say that I don't believe it's a design fault, because Apple has an obligation to be very careful about that; I also don't think it's a fault with the component(s) because it seems to be happening all over the planet and doesn't seem to be localized; so I think it's due to the use of component(s) below, or at the limit of, Apple's standards which, when put under extreme stress (higher brightness), end up failing.

I think it's already clear to everyone that this is a design or manufacturing defect in this Apple model.

So let's hope that Apple takes on this construction problem and repairs it or at least contributes part of the cost of the (overly expensive) repair of our computers.

If it were a car, surely all our computers would be called into the workshop to replace the component that has broken down or is in the process of breaking down.

As it's a computer... let's hope that Apple will behave in a way that suits its customers, who believe in the above-average Apple standard...

So keep presenting your cases to Apple.

MacBooks with FlexGate have similar problems. In the MacBook, this is caused by the LVDS cable, which is fixed to the PCB of the lcd assembly and not easily replaceable.

However, the LVDS cable in the iMac can be replaced. Has anyone had experience with this or replaced this cable before?https://www.ebay.nl/itm/255809013613?mkcid=16&mkevt=1&mkrid=1346-175129-2357-0&ssspo=9_Kc3GPRQIS&sssrc=4429486&ssuid=2ViFqcZVSqK&var=&widget_ver=artemis&media=COPY).

I want to keep attention on the ongoing “persistent horizontal lines” display problem affecting the 2021 24" M1 iMac, which seems to be spreading to other Apple chip iMac models (M1, M3, M4). As many users have observed—including in this thread and others—this issue appears to have a disturbingly high failure rate. The many reports and "me toos" confirm this is not an isolated case.

I agree that Apple faces real cost and brand reputation concerns if they acknowledge this as a design flaw. Perhaps more so from ground-up complaints and the ripple effect of avid Apple users looking elsewhere, other than Apple, like myself, a life-long Mac supporter and enthusiast.

This design flaw has existed—untreated—for several years in the iMac line. Many users, like myself, end up using external monitors or switching to Mac Mini and laptop setups to avoid expensive screen replacements, especially out of warranty.

I urge Apple not to wait until most affected iMacs are out of use before announcing a Service Program, just to minimize the impact and lingering doubts of Apple as a superior brand. The right thing to do is to provide clear and fair support for all, loyal and first-time customers, especially given the documented scale of this issue.

For other users: Keep documenting your cases here and through Apple Support. The more evidence collected, the harder it will be for this problem to be ignored.

Thank you to everyone sharing experiences and strategies for escalation—I believe it’s making a real difference for those looking for resolution.

Hi Kerdkiat,

The issue lies in an internal LCD cable itself, which overheats and ends up short-circuiting. To mitigate the problem for now, reduce the screen brightness and use an external monitor as a temporary solution. There are affordable 4K options available with brightness levels of 350 nits or more — anything below that will be noticeably inferior to the iMac’s panel. If colour accuracy matters, choose a model that supports proper calibration.

This approach gives you time to contact Apple and present your case calmly. Always remain polite, yet persistent. Explain the situation clearly and continue to insist, courteously, until you receive a concrete answer. This is a design and manufacturing issue, and in some (rare) cases Apple agrees to replace the display. However, it is well known that the problem is likely to reappear in the future, since the fault comes from the LCD module itself.

You can also purchase a new panel and replace it yourself, but the long-term outcome tends to be the same, precisely because the underlying issue remains unchanged.

If Apple does not accept responsibility, it may be wise to reconsider buying fully integrated devices. If what we truly value is the operating system, then that is what we should continue to buy — just the computer part. Mac mini is a much more inexpensive and versatile alternative.

At my company, once we became aware of this issue and of Apple’s refusal to take responsibility, we decided to sell all our iMacs and switch entirely to Mac minis. It proved to be a more reliable and sustainable approach, avoiding the recurring risks associated with integrated displays.

Displays — often of even higher quality — can be found outside the Apple universe, whether you want top-tier performance or a more budget-friendly option.

Good luck with the process.

I'm doing exactly this now. Using a second monitor, and using the Lunar app to turn off the defective main display. Apart from the display, everything else is working as it should.

I bought an imac m1 2021 and black lines started appearing then eventually this weird blotch of purple color started showing on the top left hand screen. Then it gradually got worst to the whole screen is black and the computer is unusable. I also noticed a burn mark up in tge left side of the screen where the putple blotches of color was. I just read someones post that took his computer with same problems to a repair guy to get a diagnosis of it and said something like there is a faulty cable that overheats so this explains it. Im really angry as Apple told me that can’t do anything because it’s out of warranty. I’ve been using Apple for decades and I always take care of my equipment. I use it for work feel really cheated because this computer was defected from the beginning. There was so many issues.