How to Fix It When a Second Monitor is Not Working

Get your second display up and running right

Second monitors are a crucial tool for improving productivity. If your computer can support multiple monitors, buying a second monitor is a good choice for enhancing your daily grind. However, what do you do if your new second monitor is not detected?

Common Second Monitor Problems

Second monitor troubles appear in a few common ways:

  • The second monitor does not display any content and shows a black screen.
  • The second monitor displays content at resolution other than its natural resolution.
  • The content on the second monitor suffers from artifacts not seen on the primary monitor.
  • The display is distorted, discolored, duplicated, or otherwise wrong.

The troubleshooting steps for most of these second monitor problems are essentially the same.

Causes of Second Monitor Problems

Regardless of the exact problem you experience, there are a few basic root causes of all second monitor problems:

  • The computer cannot support the display, whether in color depth, pixel count, or interface options.
  • The monitor's cable is damaged or malfunctioning.
  • The computer's display drivers aren't properly handling the secondary display.

How to Fix Second Monitor Problems on Windows and macOS

Follow the steps below to diagnose and fix the cause of these second monitor malfunctions.

  1. Restart the computer. Restarting a PC is a classic troubleshooting step because it works effectively. Restarting can solve the problem. It also closes other processes that might interfere. With a quick restart, you begin from a clean slate.

  2. Change the screen resolution. If the second monitor shows an image, but the image is blurry, pixelated, distorted, discolored, or a duplicate of the primary display, check the computer's display settings. If the frame rate or resolution is incorrect, the fix can be found in the same place. These display issues can also be fixed on macOS.

  3. Adjust the scaling settings. If the windows display as different sizes on different monitors in Windows 10, adjust the scaling settings. The recommended setting will match the apparent window size across monitors as closely as possible.

    On macOS, navigate to System Preferences > Displays. Select Default for display, or press Scaled and choose the correct resolution.

  4. Fix discoloration and color accuracy. The same works on macOS using its display calibration process. If the computer's settings don't fix the problem, use a hardware calibration device or adjust the monitor's color settings, gamma, and brightness settings in the monitor's on-screen menu. Every monitor is different, but Color or Display Depth are reliable keywords to scan for.

    Some color issues can be the result of different display panels, backlights, technologies, or age. If you need an exact match, consider professional-grade photo editing monitors.

  5. Adjust the monitor's refresh rate. Monitors are built to work at a certain refresh rate or a set of popular ones. If your computer doesn't send a signal at one of those supported rates, there's a chance the monitor won't display the signal.

    In macOS, navigate to System Preferences > Displays, and adjust the Refresh Rate drop-down menu.

  6. Swap out the current cable. If you see artifacts on the display or no picture at all, a bad cable is the most common culprit. Very long or poorly-shielded cables are especially prone to interference.

    Good cables don't need to cost a fortune. Gold-plated connectors or oxygen-free copper doesn't provide a noticeable difference in image quality. However, poorly constructed cables can lead to issues. Purchase a cable from a trusted manufacturer. Monoprice offers an excellent combination of affordability and reliable quality.

  7. Connect the second monitor's cable to an alternate port. Change the port on the PC, the port on the display, or both. Only change one at a time, so you can pinpoint which ports caused the problem. If your PC doesn't have a second compatible port, connect the monitor to a different computer. This can identify issues with the computer's settings or ports.

  8. Make sure the cable supports the correct version of the display standard. HDMI cables can support anything from HDMI 1.0, which provides minimal support, to HDMI 2.1, which can support the highest resolutions, color spaces, and audio channels.

    USB-C and Thunderbolt monitors are even more confusing since the cables are physically interchangeable but not cross-compatible. DVI, meanwhile, has multiple versions, and it's possible to plug an incompatible DVI cable into a computer or monitor.

    Look at the documentation that came with the cable or the website where you purchased the cable to learn the latest display connection version supported by the cable. If the cable doesn't support your display, replace it with a cable that does. Additionally, check the physical appearance of the cable's connectors and the connectors on the PC and monitor to ensure both are the same.

  9. Remove any switches or converters from the signal chain. If the cable has HDMI on one end and DVI on the other, try a cable that has the same connector on both ends. If possible, remove or replace dongles and switches temporarily. If the simpler connection works, the removed device is to blame. Be sure to only remove one device at a time for proper troubleshooting.

  10. Try a different display interface. For example, if the second monitor is currently connected over HDMI, use Display Port instead. This can accomplish a few things. If the current interface can't drive all the pixels in the second monitor, switching to a different interface can fix that problem.

    Based on capability, you can rank common display connectors like so: DisplayPort, HDMI, DVI, Thunderbolt, USB-C, VGA. Unless you must use a VGA connection for legacy compatibility, avoid it, as it cannot properly drive modern displays. Don't forget there are multiple versions of HDMI, DVI, and USB-C. Just because you can plug a cable into a port doesn't mean you'll have full compatibility.

  11. Update the computer's display drivers. If you have a third-party discrete graphics card, update the drivers from the manufacturer. If you plug the monitor into the motherboard's display connectors, visit the motherboard or computer manufacturer's website to see if there are any updated drivers for those features.

  12. Lower the image quality. If the monitor suffers from a poor frame rate, choppiness, or corrupted video or game content, reducing the signal's complexity can help. For games, try the lowest-quality settings first, then gradually improve the quality until the issue reappears. For video content, try a lower resolution or a less-demanding frame rate.

  13. Check the power connections. If the monitor doesn't turn on, try different power connectors or wall outlets. Test wall outlets with other devices before plugging in the monitor to ensure those devices work properly.

  14. Check the monitor's input settings. If the monitor has multiple input interfaces, make sure you have the correct one selected in the monitor's on-screen menu. Most monitors have an auto-detect feature that automatically switches to the connector receiving the signal. When that doesn't work, set the display connector manually.

  15. Make sure the monitor can display the content sent to it. Does the monitor have sufficient color gamut, resolution, or bit depth to display the content properly? Consult the monitor's documentation or the monitor manufacturer's website.

  16. Replace the monitor. If none of these steps fix the problem, you may need to replace the monitor. If you see colored lines, black or colored points, or cracks in the image, the monitor's panel may be damaged, which requires replacement.

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