Why Do Black Horizontal Lines Appear on iMac Screens?
There are several possible reasons behind this display problem. Some of the most common include:
- Graphics card issues – A malfunctioning GPU can cause display artifacts such as lines.
- Loose or damaged display cables – Connection problems inside the iMac may affect visuals.
- Software bugs – A macOS glitch or outdated update may lead to temporary screen errors.
- Overheating – Prolonged use in hot environments (common in Dubai) may stress the graphics system.
- Hardware failure – Issues with the screen panel or backlight.
Quick Checks Before Troubleshooting
Before moving to advanced steps, try these simple checks:
- Restart your iMac and see if the lines disappear.
- Update to the latest macOS version.
- Connect your iMac to an external monitor. If the external display works fine, the issue may be with your iMac’s internal screen.
Step-by-Step Fixes for Black Horizontal Lines
1. Reset NVRAM/PRAM
Corrupted memory settings often cause display issues.
- Shut down your iMac.
- Turn it on and press Option + Command + P + R for 20 seconds.
- Release the keys and restart.
2. Reset SMC (System Management Controller)
For Intel-based iMacs, resetting the SMC can solve display-related issues.
- Shut down your iMac.
- Unplug the power cable for 15 seconds.
- Plug it back in and restart.
(For Apple Silicon iMacs, a simple restart usually resets these controls.)
3. Boot into Safe Mode
Safe Mode disables third-party apps that might be causing screen conflicts.
- Restart while holding Shift.
- Log in and check if the lines still appear.
- If the screen looks fine, uninstall recently added apps.
4. Check for macOS Updates
Outdated software can trigger graphics issues.
- Go to System Settings > General > Software Update.
- Install the latest version.
5. External Display Test
Connect your iMac to another monitor.
- If the external monitor shows no lines, the issue may be hardware-related in your iMac screen.
- If both screens show lines, the GPU might be failing.
6. Run Apple Diagnostics
Apple’s built-in tool can help detect faulty hardware.
- Restart your iMac and hold down D.
- Follow the on-screen steps.
Comparison Table – Causes & Solutions
| Possible Cause | Fix |
| Outdated macOS | Update to the latest version |
| Corrupted memory settings | Reset NVRAM/PRAM and SMC |
| Third-party app conflict | Boot into Safe Mode, remove problematic apps |
| Loose/damaged display cable | Seek professional repair in Dubai |
| Failing GPU or screen panel | Run Apple Diagnostics and arrange professional replacement |
When to Seek Professional Help in Dubai
If black horizontal lines persist after all troubleshooting steps, it is likely a hardware issue. Common culprits include failing graphics cards, damaged display panels, or internal cable problems.
At this stage, professional repair is essential. At Azizi Technologies UAE, our certified technicians in Dubai provide expert diagnostics and reliable repairs, ensuring faulty components are replaced with genuine parts. With our help, your iMac can be restored to smooth performance without added risks.
Tips to Prevent Screen Issues in the Future
To keep your iMac’s display running smoothly:
- Always keep macOS updated.
- Avoid overheating and use your iMac in a cool, ventilated space.
- Do not overload your iMac with heavy apps running simultaneously.
- Schedule regular maintenance with a professional service in Dubai.
Why Choose Us for iMac Repairs in Dubai?
We understand how important your iMac is for work, study, and entertainment. That is why we offer reliable repair solutions tailored to Apple devices.
- Expert Technicians – Specialists trained in diagnosing complex display issues.
- Fast Turnaround – Quick fixes to minimize downtime.
- Genuine Parts – Only original Apple components used.
- Accessible Locations – Serving customers across Marina, Downtown, JLT, and Business Bay.
Final Thoughts:
Black horizontal lines across your iMac screen may look like a serious problem, but in many cases, the cause is a minor glitch that can be fixed with resets, updates, or safe mode troubleshooting. Testing with an external display is also a quick way to confirm whether the issue is software or hardware.
If the lines do not go away, do not delay seeking expert help. At Azizi Technologies UAE, we provide professional iMac repair services in Dubai, ensuring your device is restored to perfect working condition so it can continue supporting your daily productivity without interruptions.
