M1 iMac Horizontal Display Lines Blamed on Bad Cable

Reports of Apple’s 24-inch M1 iMac developing dark, horizontal lines on the display after a couple of years of use have been have been flooding the Apple Support Community, Reddit, and other forums for several months now. One affected user’s investigation into the issue has revealed that a bad flex cable could be to blame (via Tom’s Hardware).

According to the user’s analysis, the display failure can be traced back to a flex cable that must carry a voltage of around 50 volts when the screen brightness is cranked up. Over time, this supposedly causes the connector to burn, resulting in short circuits that cause dark lines to appear all over the iMac’s screen.

The sleuth concluded that this could be the result of a design flaw, a manufacturing defect, or subpar components from Apple’s supplier.

An Apple Support Community thread about the issue that was started in October 2023 has amassed 17 pages of disgruntled responses from affected users. Most users reported seeing horizontal lines on their iMac’s screen 18-24 months after purchase, long past Apple’s standard one-year warranty.

Apple’s service centers deem this issue an irreparable malfunction, with the only available course of action being a screen replacement. For those without AppleCare+ extended coverage, an out-of-warranty iMac screen replacement can cost around $600-700 USD.

If the faulty flex cable really is what’s causing these display failures and Apple has continued to use the same design, this issue could cross generational lines and affect later iMac models too. At least one owner of an M3 iMac, purchased in May 2024, reported seeing similar lines on their All-in-One’s display.

Apple’s M2 and M3 iMacs not being as old yet could explain why this issue isn’t as widespread among them. In comparison, the original M1 iMac came out back in May 2021.

Apple has yet to officially acknowledge this issue as a manufacturing defect. While some users have had success in getting Apple to replace their faulty M1 iMac screens for free, others have had to pay for the repairs. In the past, Apple has taken responsibility for design flaws and manufacturing defects by offering free repairs/replacements.