Monitor Flickering and Going Black: 3 Real Fixes That Work

Cause #1: A Bad or Loose Cable (Most Common)

I know this error is infuriating—your screen blinks out for a second, then comes back, then does it again. Nine times out of ten, the culprit is the cable between your monitor and your PC. It's not glamorous, but it's true.

This happens with older HDMI cables, cheap DisplayPort cables, or any cable that's been yanked one too many times. I've seen it on Dell U2720Q monitors and LG 27GL850s alike. The signal degrades, and the monitor loses sync, so it goes black for a split second. Sometimes it flickers at 60Hz but not at 30Hz—that's a dead giveaway.

The Fix

1. Unplug both ends of the cable. Check for bent pins or melted connectors.
2. Reseat it firmly—you should hear a click.
3. If the flicker continues, swap the cable. Don't use the one that came in the box unless it's brand new. Buy a certified HDMI 2.1 or DisplayPort 1.4 cable—they're cheap and they handle higher bandwidth better.
4. Test with a different port on both the monitor and the GPU. Some ports die first.

If you're on a laptop and using a USB-C to HDMI adapter, that adapter is a common failure point too. Try bypassing it with a native HDMI port if you have one.

Cause #2: Refresh Rate Set Too High for Your Cable or Port

Your monitor might advertise 144Hz, but if you're running an older HDMI cable (like HDMI 1.4), it can't carry that signal reliably. The result? Flicker, black screens, or the monitor randomly dropping to 60Hz.

This one bit me a few years ago with an ASUS VG248QE. I had a brand new monitor, a solid GPU, but an ancient HDMI cable from a printer box. The screen would go black every time I opened a game. Switching to DisplayPort fixed it instantly.

The Fix

1. Right-click your desktop and open Display settings (Windows 10/11) or System Settings > Displays (macOS).
2. Scroll down to Advanced display settings (Windows) or the refresh rate dropdown (macOS).
3. Lower the refresh rate one step—from 144Hz to 120Hz, or from 60Hz to 59Hz on a TV.
4. See if the flicker stops. If it does, you've found your ceiling for that cable.

Then go buy a better cable. A good DisplayPort 1.4 cable handles 144Hz at 1440p without breaking a sweat. If you're using an HDMI 2.0 port, make sure the cable is certified for HDMI 2.0 or higher. Don't trust the sticker on the cable—check the specs.

Cause #3: Power Delivery Issues (Intermittent Power Loss)

Sometimes the monitor isn't losing signal—it's losing power. You'll see the screen go black, then the power LED blinks or goes off completely for a second before coming back. This is more common on monitors with external power bricks, but it also happens on built-in power supplies.

The trigger could be dirty power in your home, a dying power brick, or a loose barrel connector. I've fixed a few of these where the issue was just a power strip with too many devices plugged into it.

The Fix

1. Unplug the monitor from the wall or power strip for 30 seconds, then plug it back in. This resets the power supply's protection circuit.
2. Plug the monitor directly into a wall outlet, not a power strip. If it stops flickering, your strip is the problem.
3. Check the barrel connector on the back of the monitor—it should be snug. Wiggle it gently. If the screen flickers when you wiggle it, the connector is loose and may need soldering or a new jack.
4. If you're using a power brick, feel it after an hour of use. If it's painfully hot, that's a red flag. Replace it with a matching voltage and amperage brick—don't cheap out, because a wrong brick can fry the monitor.

In my experience, power-related flicker tends to be random—it'll happen every few minutes, not in a pattern. Cable issues usually happen when you move the monitor or bump the desk. Refresh rate issues happen under load. That pattern recognition will save you time.

Quick-Reference Summary

Start with the cable. It's the cheapest fix and the most common cause. If that doesn't do it, move to the refresh rate. And if you've tried both and the screen still goes black, suspect power. You'll save yourself a service call.