Monitor Display Problems: Diagonal Lines

By Jane Williams

Monitor display problems manifest in various ways, including strange vertical, horizontal and diagonal lines. The appearance of unusual lines along the length of your monitor generally indicates a problem with one of three components: the video cable, the video card or the monitor itself. Troubleshooting is fairly straightforward and can help narrow down the true culprit quickly.

Troubleshoot With Second Monitor

Although not required, a second monitor can help quickly test and eliminate the possible causes for your diagonal lines. Disconnect the original monitor and use the same cables to connect the second test monitor. On laptops, simply connect the second monitor as an external device. If the second monitor shows the same diagonal lines, the original monitor is most likely not the problem. A clear picture on the second monitor indicates that the first monitor may be faulty, requiring repair or replacement.

Faulty Video Cable

A simple cause of monitor problems is a damaged or loose video cable. Cable connections are easy to check on desktop computers, but in laptops it involves fairly in-depth disassembly. Use your laptop's service guide to properly access each end of the video cable. Verify that each end of the cable is securely fastened to its appropriate connection point. Check the cord for signs of wear or damage and watch the monitor as you wiggle the cord to see if the lines change or disappear. If wiggling the cord affects the lines, the cord may be faulty and require replacement.

Faulty Monitor

A faulty monitor can cause odd screen behavior, resulting from a power surge, magnetic interference or water damage. If the fault lies with the monitor, a second test monitor will not display the diagonal lines when connected. Depending upon your computer and monitor type, you can either have the screen replaced, such as with laptops, or purchase a new monitor for your desktop.

Video Card Failure

Video cards, also known as graphics cards, translate the data provided by your computer into the digital imagery you see on the screen. If this card suffers damage, from a power surge or liquid spill, it can result in odd video displays and effects. Graphics cards in desktop computers are easily replaced by simply exchanging the failed one for a new one, but the cards in laptops are integrated into the motherboard. A failed laptop graphics card necessitates the full replacement of the entire motherboard as a result.