Fix: Monitor Randomly Loses Signal but the PC Stays On

A monitor that suddenly shows “No Signal” or goes black while the computer keeps running, fans spinning and lights on, is usually a display-link problem rather than a dead PC. The cause is most often a loose or marginal cable, a refresh-rate or bandwidth mismatch, a graphics driver reset, or a power-saving feature that drops the link. Start with the cable and port, then move to Windows display settings and the driver. Most people sort it out in under an hour. This guide applies to desktop PCs and laptops with external monitors on Windows 11 24H2 and 25H2.

Quick Answer

• Power off the monitor, reseat both ends of the video cable, and try another cable or port on the graphics card.
• Lower the refresh rate in Settings, System, Display, Advanced display and turn off HDR to see if the drops stop.
• Press Win+Ctrl+Shift+B the next time the screen goes dark to reset the graphics driver without restarting.
• Check Event Viewer for a “Display driver stopped responding” entry (Event ID 4101) to tell a driver reset from a cable fault.
• Reinstall the graphics driver with the clean-install option from the NVIDIA, AMD or Intel installer.

Before You Start

Work out what kind of blackout you have, because the fix differs. Pay attention to what happens in the moment.

• If the screen blinks for a few seconds and returns with your windows intact, a driver recovery or a link retrain is likely.
• If the screen stays black but sound still plays and the keyboard lights respond, the PC is awake and only the display link is down.
• If the PC itself restarts or freezes, you have a different problem, often power delivery or overheating, and the steps here only partly apply.
• If the “No Signal” message also appears at the motherboard logo or in the BIOS, Windows is not the cause. Focus on cables, ports and hardware.

Safety notes: shut down and unplug the PC before touching internal power connectors. The registry change in the last method can affect stability, so export a backup before editing. Write down your current monitor model, resolution and refresh rate, so you can restore them later.

Method 1: Rule Out the Cable, Port and Monitor

1. Turn off the monitor and the PC. Unplug the video cable at both ends.
2. Check the connectors for bent pins, dust or a loose fit. Plug the cable back in until it clicks or seats fully.
3. Connect the cable to the graphics card output, not the motherboard video port. If the monitor is plugged into the motherboard while a graphics card is installed, move it.
4. Try a different port on the card, and switch between DisplayPort and HDMI if both are available.
5. Swap in a different cable known to be good. Long or older cables are a common cause when the screen runs a high refresh rate or high resolution.
6. Remove adapters, docks, KVM switches and extension cables from the chain while testing, then add them back one at a time.
7. Open the monitor’s on-screen menu and set the input manually instead of Auto. Look for a DisplayPort version option and set it to 1.2 if blackouts continue on 1.4, or the other way round on your model.
8. Test the monitor with another PC or a laptop. If it still drops there, the monitor or cable is at fault.

This works because a video link negotiates a speed when it starts, and a weak connection can lose that agreement mid-session. A better cable or a lower-demand mode keeps it stable.

Method 2: Adjust Windows Display and Power Settings

1. Open Settings, then System, then Display, then Advanced display.
2. Pick your monitor and use Choose a refresh rate to select a lower value, such as 60 Hz. Keep the resolution at native.
3. Back on the Display page, turn Use HDR off for the affected monitor.
4. Open Graphics, then Change default graphics settings, and turn off variable refresh rate options one at a time if blackouts happen mainly in games.
5. Disable Fast Startup: open Control Panel, Power Options, Choose what the power buttons do, Change settings that are currently unavailable, then clear Turn on fast startup.
6. In Power Options, choose Change plan settings, then Change advanced power settings. Under PCI Express, set Link State Power Management to Off.

If the problem stops at a lower refresh rate, the link is probably running at the edge of what the cable or port can carry. Try raising the refresh rate in steps to find the stable ceiling, or replace the cable with one rated for your mode.

Method 3: Reset and Reinstall the Graphics Driver

1. When the screen next goes dark, press Win+Ctrl+Shift+B together. You should hear a short beep and the display should flicker back within a few seconds. This restarts the graphics driver without closing your apps.
2. Open Event Viewer: search for it, then go to Windows Logs, System, and look for Event ID 4101 or a source named nvlddmkm (NVIDIA), amdkmdag (AMD) or igfx (Intel) around the time of each blackout.
3. Download the current driver from the NVIDIA, AMD or Intel support site, choose the custom or clean installation option, and let it finish. Restart afterward.
4. If the problem began right after a driver update, install the previous version from the vendor’s archive instead.
5. Return any graphics overclock, undervolt or memory profile to stock while you test, because unstable settings produce the same symptoms.

Windows watches the GPU for operations that run too long, a feature called timeout detection and recovery. By default it waits two seconds before resetting the graphics stack, which is what produces the dark flicker and the 4101 entry. Seeing it repeatedly points to a driver, overheating or hardware-stability issue instead of the cable.

Method 4: Extend the Timeout as a Last Diagnostic Step

1. Press Win+R, type regedit, and press Enter. Export a backup with File then Export.
2. Go to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\GraphicsDrivers.
3. Create a DWORD (32-bit) Value named TdrDelay and set it to 8 (decimal).
4. Restart and see whether the blackouts change.

Treat this as a way to learn more, not a repair. It gives a slow GPU extra time before Windows resets it, so it can hide the symptom while the real cause remains. If the crashes stop, still look into temperatures, power cables and driver versions. Delete the value to return to the default.

If It Did Not Work

• Blackouts continue on every cable and port: reseat the graphics card and its power connectors with the PC off and unplugged, and check that each power cable is fully clicked in.
• Event ID 4101 repeats under load: monitor GPU temperature with the vendor’s overlay and clean dust from heatsinks and fans. Overheating or an unstable overclock commonly triggers resets.
• Blackouts only after the PC sleeps: set the monitor input manually, disable monitor deep sleep options in its menu, and update the BIOS if the board maker lists display or sleep fixes.
• The PC restarts or freezes too: look in Event Viewer for Kernel-Power Event 41 and open Reliability Monitor (run perfmon /rel) to see what failed. Test the power supply and memory next.
• Only one monitor in a multi-monitor setup drops: swap which monitor uses which port. If the fault follows the monitor, replace its cable or inspect the monitor itself.
• Still stuck: try another graphics card or integrated output if you have one. If the symptom disappears, the card needs a warranty check.

Common Questions

Why does the monitor lose signal but the PC keeps running?

The computer and the video link are separate. A cable fault, a refresh-rate mismatch or a graphics driver reset can interrupt the display link without stopping Windows. That is why sound and keyboard lights often keep working.

Can a cheap cable really cause this?

Yes. At high resolutions and refresh rates the cable must carry a lot of data, and a marginal one may work for days then drop. Swapping it is the lowest-cost test.

Is Win+Ctrl+Shift+B safe to press?

It is built into Windows and only restarts the graphics driver. You may see a brief flicker and hear a beep, and open apps should stay open. It does not reinstall anything or fix a damaged cable.

Should I change TdrDelay permanently?

Usually not. It delays recovery and can hide a fault that deserves attention. Use it to diagnose, then fix the underlying driver, heat or power issue.

Could my power supply be the cause?

It can, especially if the graphics card is demanding. If the blackouts coincide with game loads and the PC may also restart, check the power connectors and consider testing with a known-good supply.

Update History

• October 14, 2026 – Initial publication; steps checked against Windows 11 24H2/25H2 and current driver releases.
• Menus can differ slightly by Windows build, BIOS vendor and driver version; check your own screens against the steps.

Sources

• Microsoft Learn documentation on WDDM timeout detection and recovery
• NVIDIA and AMD support and community guidance on display signal loss and clean driver installation
• Technology publisher guides on display signal loss and the Windows graphics driver reset shortcut