How to Test a Computer Monitor That Isn't Working

Check to make sure it's on! Some monitors have more than one power button or switch—confirm that they're all switched on.

Check for disconnected monitor power cable connections. Your monitor might be working fine and your only problem may be a loose or unplugged power cable.

Also be sure to check for any cable adapters that aren't fully secured, such as a small connector that joins an HDMI or DVI cable to a VGA plug, or vice versa.

A disconnected monitor power cable could be the cause of your problem if your monitor's power light is completely off.

Check for disconnected monitor data cable connections. Again, your monitor might be turning on without a problem but no information can get to it because the cable that connects it to your computer is disconnected or loose.

A disconnected data cable could be the cause of your problem if your monitor's power light is on but is amber or yellow instead of green.

Turn the monitor's brightness and contrast settings completely up. It might be showing information but you just can't see it because these display settings are too dark.

Most modern monitors have a single on-screen interface for all settings, including brightness and contrast. If it turns out that your monitor isn't working at all then you'll likely not have access to this interface. An older monitor might have manual knobs for adjusting these settings.

Make sure all monitors are set up properly (if this is a dual-monitor setup). This step might seem too general, but if you're using two or more monitors, it's possible that the extended displays work just fine but the operating system isn't using them properly.

This could be due to a number of things like a missing/corrupt video card driver or an incorrect setup procedure. For example, maybe a projector is connected to the laptop but not set up as an additional screen (so it remains black), or maybe the projector is configured as the primary display, and so the on-board screen is black.

Test that your computer is working correctly by connecting to your PC a different monitor that you're certain is working properly. Your monitor might be fine but your computer might not be sending information to it.

If the new monitor you connected doesn't show anything either, proceed to Step 7.

If the new monitor you connected does show information from your computer, proceed to Step 8.

When testing with the new monitor, make sure you use the data cable that came with it and not the one from your original monitor.

Determine why your computer isn't sending information to your monitor. Since neither monitor works, you now know that the computer isn't sending information to the monitor. In other words, you've proven that your computer, not the monitor, is the reason that nothing shows up on the screen.

Chances are your original monitor is working fine but something else is to blame, like a disconnected or faulty video card, for example.

Test your original monitor with a monitor data cable that you know is working. It's possible that the monitor itself is working properly but it can't receive information from the computer because the cable that connects the monitor to the PC is no longer working.

If possible, test using the data cable from the monitor that you successfully tested earlier. If not, purchase a replacement monitor data cable to test with. The data cable on some older monitors are permanently connected to the monitor and aren't replaceable. In these cases, you'll have to skip this step and replace the monitor.