Computer Screen Says No Signal: Causes and Fixes

Introduction: Why Does My Computer Screen Say "No Signal"?

Seeing "No Signal" pop up on your display is one of those moments that makes you want to just start unplugging things and hoping for the best. But before you do that, it helps to understand what that message is actually telling you: your screen isn't detecting a usable video signal from your computer. That's it. It's not necessarily a verdict on whether your screen — or your PC — is broken.

The tricky part is that a computer screen no signal message can come from either side of the connection. Your PC might not be starting up properly. The graphics card might not be outputting anything. The video cable could be loose or damaged. You might have the wrong input selected. Or the computer could be running just fine while Windows, a driver, or a display setting is quietly getting in the way.

This guide takes a different angle than a general monitor troubleshooting checklist. Here, the goal is to answer one specific question:

Is the computer not sending a signal, or is the screen simply not receiving one?

Once you know which side of that equation you're dealing with, the fix gets a lot easier to find. And if you've already worked through cable and input basics and want the full step-by-step monitor-side checklist, our guide to PC Monitor Says No Signal? 15 Ways to Fix It covers that in detail. This article picks up the thread from the computer's perspective.

Step 1: Is It the Computer or the Screen?

Before you touch a single cable, run through a few quick questions. This is the fastest way to start narrowing things down, and it keeps you from taking anything apart before you actually need to.

• Does the PC power on at all?
• Does the monitor itself turn on (even if it's just showing "No Signal")?
• Is the monitor actually displaying "No Signal," or is it completely blank/off?
• Does the keyboard respond when you press a key?
• Do you hear normal startup sounds from the PC?
• Can a different device display something on this same screen?

A simple pattern starts to emerge from these answers:

Monitor turns on and works, but the PC isn't sending video → this points to a PC-side problem.

PC seems to be running fine, and another device works on this screen → this points to a cable, input, or PC output issue specifically.

Step 2: Check Whether the PC Actually Started

This is one of the biggest differences between troubleshooting a pc screen no signal situation and just assuming the monitor is broken. A lot of people hear their case fans spinning and assume the computer has booted — but that's not necessarily true.

Check for:

• The power LED on the case
• Case fans running steadily (not just a brief spin and stop)
• Keyboard and mouse lights turning on
• Any connected USB devices powering up
• Normal startup beeps or chimes
• Motherboard diagnostic LEDs, if your board has them

Here's the key thing to remember: fans spinning does not always mean the computer has successfully booted. A PC can be drawing power and running its fans while getting stuck partway through startup — and if it never finishes that process, there's no video signal to send anywhere.

Step 3: Check the Keyboard With Num Lock or Caps Lock

This is a genuinely useful trick that anyone can do without opening the case. Press Num Lock or Caps Lock on your keyboard and watch the indicator light.

If the light responds — it turns on, off, or toggles normally — that's a solid sign your PC has actually powered up and is running, even if the computer screen not displaying anything. The problem is more likely with video output rather than the PC failing to start at all.

If there's no response whatsoever, that points toward a deeper issue: the PC may not have completed startup, or you could be looking at a RAM problem, a GPU problem, a motherboard issue, or some other piece of hardware that's preventing the system from getting anywhere.

Step 4: Does the BIOS or Startup Logo Appear?

This is one of the most valuable diagnostic checks in this entire guide, because it splits your problem cleanly into two very different categories.

Situation A: You can see the BIOS screen or manufacturer logo, but then Windows loads and the signal disappears. This points toward something in Windows itself — display settings, an unsupported resolution or refresh rate, or a graphics driver conflict.

Situation B: There's no signal from the very moment you power on the PC. This points more toward the cable, the GPU, RAM, the motherboard, other PC hardware, or the video output being connected to the wrong port.

Take a moment to actually watch your screen through a full restart before assuming anything — this one detail changes your entire troubleshooting direction.

Step 5: Check the Video Cable and Input Source

We won't rebuild the full cable-and-input walkthrough here since that's covered step by step in our monitor-focused guide, but it's still worth a quick pass:

• Check your HDMI, DisplayPort, or USB-C connection
• Confirm the monitor is set to the correct input source
• Make sure the cable is firmly seated on both ends
• Try a different port if one's available

If you're seeing a screen no signal detected message, a computer screen says no input alert, or a PC screen says no input prompt, this is usually where to start — these messages are just different wordings for the same underlying issue.

Step 6: Make Sure the Cable Is Connected to the GPU

This deserves its own callout because it's a genuinely common mistake, especially after a PC has been moved, rebuilt, or cleaned. If your desktop has a dedicated graphics card, your monitor cable needs to go into the GPU's video output — not the motherboard's built-in HDMI or DisplayPort.

If your desktop has a dedicated graphics card, the motherboard's video port may not provide an active display output at all.

This single mix-up perfectly explains a lot of pc screen showing no signal, pc screen no signal detected, and computer display no signal situations where every cable looks properly connected but nothing shows up — because technically, nothing was ever being sent from that port in the first place.

Step 7: Check the Graphics Card

If you're not seeing a BIOS screen at all, it's time to check the GPU itself:

• Confirm it's fully and properly seated in its slot
• Check that power connectors are firmly attached
• Make sure the GPU's fans are spinning
• Confirm you're plugged into one of the GPU's actual outputs
• Consider whether you recently installed, cleaned, or moved anything inside the case

This is especially worth focusing on if your PC screen suddenly says no signal right after installing a new GPU — that's a classic sign of a card that isn't fully seated or a power connector that didn't get plugged all the way in.

Step 8: Check RAM if There Is No BIOS Display

If your PC powers on but you're not getting any BIOS screen or startup logo at all, RAM is worth investigating next.

• Shut the PC down completely and disconnect it from power
• Reseat your RAM sticks
• If you have more than one stick installed, try running the PC with just one at a time

One important note here: only open up your PC if you're comfortable working with internal hardware. If you're not, this is a reasonable point to call in some help rather than push further on your own.

Step 9: What If the PC Has Sound but No Picture?

Here's a scenario a lot of people run into: you hear the Windows startup sound clearly, everything sounds normal, but the screen stays completely black and still says "No Signal."

This tells you something important — the PC is likely running normally, but video output specifically is failing. At this point, focus your attention on:

• The GPU's output
• The video cable
• The monitor's selected input
• The graphics driver
• Resolution and refresh rate settings

The fact that you're hearing sound is actually good news — it rules out a huge chunk of possible causes and narrows things down to the video path specifically.

Step 10: What If Windows Is Running but the Screen Says No Signal?

If you're confident Windows has actually loaded — maybe you can hear notification sounds, or a second monitor is still working — prioritize checking:

• The graphics driver
• Display resolution
• Refresh rate
• Multiple-display settings
• Which output Windows currently thinks is active

One quick trick worth trying: press Win + Ctrl + Shift + B. This forces Windows to reset the display driver without a full restart, and you'll typically hear a short beep along with a brief flicker as it reloads.

Step 11: Try Windows Display Shortcuts

If you're fairly sure the PC has made it into Windows, try pressing Win + P to bring up the display-switching menu, then cycle through:

• PC screen only
• Duplicate
• Extend
• Second screen only

It's more common than you'd think for a computer to end up outputting video to the wrong display entirely, especially after a Windows update or a change to your monitor setup. This is directly relevant if you're dealing with computer screen not detecting PC or a general PC display not showing situation — sometimes the display is working perfectly, just not the one you're looking at.

Step 12: Test Another Display

This is one of the most useful diagnostic moves you can make. Connect your PC to a different monitor, a TV, or a portable monitor if you have one available.

PC works fine on another display → the problem is more likely your original screen, its cable, or the input being used.

Every display you try shows no signal → the problem is more likely coming from the PC, the GPU, RAM, or a Windows setting.

Treat this step as a major fork in the road for your troubleshooting — it tells you almost immediately which direction to focus on next.

Step 13: Test the Screen With Another Device

Flip the test around. Connect your screen to a laptop, a different PC, a game console, or another HDMI or USB-C device.

If the screen displays normally → the screen itself is probably fine, and the issue is on the original PC's side.

If it still shows no signal → shift your focus to the input, the cable, the port, or the monitor's own hardware.

Step 14: When Is the Problem Most Likely the PC?

Here's a quick reference table to help you connect what you're seeing to the most likely cause.

Situation	Likely Problem
PC won't power on at all	PC hardware
No BIOS logo appears	GPU, RAM, or motherboard
BIOS works but Windows doesn't display	Driver, resolution, or Windows settings
Windows startup sound plays but no picture	GPU, driver, or cable
Another monitor also says No Signal	PC-side issue
Same monitor works fine with another PC	Original PC or output issue
A different cable fixes the problem	The old cable
A different input fixes the problem	The original port or input

Step 15: When Should You Contact a Technician?

At a certain point, continued DIY troubleshooting stops being productive. It's worth bringing in professional help if you're dealing with:

• No BIOS display at all, even after checking RAM and GPU
• Multiple monitors that all fail to show anything
• A GPU that appears to have failed
• RAM troubleshooting that hasn't changed anything
• Motherboard diagnostic LEDs showing an error code
• A PC that keeps shutting down unexpectedly
• Any burning smell or visible physical damage
• A PC that stopped displaying right after a hardware upgrade, with no obvious fix

None of these are things you need to force your way through alone, and pushing forward without the right tools can sometimes turn a fixable issue into a more expensive one.

Final Quick Diagnosis

If you want the short version, walk through this:

Computer Screen Says No Signal? Start Here

1. Does the PC power on? If not, focus on PC hardware.
2. Does the keyboard respond? (Try Num Lock.) If not, suspect RAM, GPU, or motherboard.
3. Can you see the BIOS screen? If not, check GPU and RAM.
4. Does the signal drop specifically when Windows loads? Check resolution, refresh rate, and graphics driver.
5. Test another cable.
6. Test another display.
7. Test the original screen with another device.

By the time you've worked through these seven checkpoints, you'll almost always know which side of the connection — PC or screen — is actually responsible.

Frequently Asked Questions

Why does my computer screen say no signal?

It typically means the screen isn't receiving a usable video signal, which can be caused by the PC not finishing startup, a GPU issue, a loose or damaged cable, an incorrect input source, or a Windows display setting.

Why does my PC screen say no input?

"No input" and "no signal" refer to the same underlying issue — the screen's currently selected input isn't receiving a video signal, often because of a cable, port, or input-source mismatch.

Why is my computer screen not displaying anything?

This can happen if the PC hasn't fully powered on, if the GPU isn't outputting video, if the cable or input is wrong, or if Windows is sending the display output somewhere other than the screen you're looking at.

Why does my PC screen show no signal but the computer is running?

This usually means the PC has powered on and may even be running fans and lights normally, but either it hasn't completed startup, or the video output specifically — through the GPU, cable, or driver — isn't reaching the screen.

Why does my computer display have no signal?

Common causes include an incorrect input source, a disconnected or faulty cable, a GPU that isn't seated properly, or a Windows display setting like resolution or refresh rate that the screen doesn't support.

How do I know if the problem is my PC or monitor?

Test your monitor with a different device, and test your PC with a different display. If the monitor works with another device, the PC is likely the issue; if the PC works with another monitor, the original screen is likely the issue.

Why does my PC have sound but no display?

This usually means the computer itself is running normally, but something specific to video output — the cable, GPU, driver, or monitor input — is failing along the way.

Why is there no display before BIOS?

If there's no signal even before the BIOS screen appears, the issue is more likely hardware-related — check the cable, the GPU, and RAM before assuming it's a Windows or software problem.

Why does my screen say no signal after Windows starts?

This points toward a software-side cause, such as a graphics driver conflict, an unsupported resolution or refresh rate, or a multi-display setting that's sending output to the wrong screen.

Can a bad GPU cause a computer screen to say no signal?

Yes. A GPU that isn't properly seated, isn't receiving power, or has failed outright can prevent any video signal from reaching the screen, even if the rest of the PC appears to be running normally.