The short version
- 01Press the monitor’s menu button — a menu proves the panel and backlight work.
- 02Unplug the video cable and look for the monitor’s built-in self-test pattern.
- 03On a desktop, move the cable to the graphics card’s own output.
- 04Step through every input on the monitor, pausing on each.
- 05Press Windows+P and select Extend, then Windows+Ctrl+Shift+B to reset the driver.
- 06Test the monitor on another computer to clear it completely.
Start here
Press the monitor’s own menu button first
Press the menu or settings button on the monitor itself. If its on-screen menu appears, the panel, the backlight and the monitor's electronics are all working, and the fault is upstream — the cable, the port, or which output the computer is actually driving. On a desktop with a graphics card, the single most common cause is the cable being plugged into the motherboard's video port instead of the card's, which produces a permanent No Signal on an otherwise perfect setup.
Applies to: Desktop and laptop monitors from Dell, HP, LG, Samsung, ASUS, BenQ and others, over HDMI, DisplayPort, USB-C and DVI, on Windows and macOS. Menu names differ by manufacturer; the input-source and self-test conventions below are common to most.
What does the monitor show?
No Signal on a monitor is a useful message because it proves the monitor is powered and running. That narrows the search to everything between the computer's graphics output and the monitor's input, which is a short list you can work through without tools. Change one thing at a time and check after each — and on a desktop, check which physical socket the cable is in before anything else.
The monitor’s own menu appears
Is the cable in the graphics card, not the motherboard?
Check the portIt says No Signal on every input
Does the computer output to anything else?
Check the computerNothing at all, no menu, no light
Is the monitor actually powered?
Check powerIt worked until you changed something
Was it a cable, a resolution, or a driver?
Undo the change1. Prove the monitor is alive
Press the monitor's menu button and look for its on-screen display. That menu is generated by the monitor itself with no input from the computer, so if it appears you have proved the panel, the backlight, the power supply and the monitor's own board are all working. Nothing inside the monitor needs fixing, and everything below is about what is reaching it.
Most monitors also have a self-test or diagnostic mode that runs with the video cable disconnected — Dell and HP both build one in, usually shown as a floating coloured box or a message confirming the monitor is working but receiving no signal. Unplug the video cable entirely and see what appears. A monitor that displays its self-test pattern with no cable attached has cleared itself completely.
If there is no menu and no power light at all, the problem is power rather than signal. Check the power cable at both ends, try a different outlet, and on monitors with an external power brick check that the brick's own light is on. A power light that glows amber or orange rather than white or blue usually means standby — the monitor has power and is not receiving video, which puts you back in the No Signal case rather than a dead monitor.
An amber or orange power light is a signal problem, not a power problem. It means the monitor is awake and waiting for video, which is the same state as an explicit No Signal message.
2. On a desktop, check which socket the cable is in
This is the answer often enough to belong second rather than buried later. A desktop PC with a dedicated graphics card has two sets of video outputs: the ones on the card, which sit lower down and horizontally on the back of the case, and the ones on the motherboard's rear panel, grouped with the USB and network ports. On most systems the motherboard outputs are inactive when a graphics card is installed, so a cable plugged into them produces a permanent No Signal.
It is an easy mistake to make and an easy one to fix. The motherboard ports are more accessible and are often at a more convenient angle, so cables end up there — particularly after moving a machine, or when someone helpful plugs it in. Move the cable to the graphics card's own output and the picture usually returns immediately.
Then confirm the monitor is set to the input you are using. Monitors do not always auto-detect reliably, and a monitor left on DisplayPort with the cable in HDMI will report No Signal indefinitely. Use the monitor's input or source button to step through every input in turn, pausing a couple of seconds on each — some need a moment to detect a signal before giving up.
Desktop with a graphics card
Use the card's outputs, lower on the case. The motherboard's ports are usually inactive when a card is fitted.
Laptop or all-in-one
There is only one set of outputs, so skip this — go to the cable and the display mode instead.
3. Cable and port, one variable at a time
Microsoft's guidance is the right discipline here: make sure the cable connecting the PC to the monitor is secure, then try changing the cable to see whether a new one works, and if the system has more than one video output port, try plugging the monitor into another one. Change one thing per test so a success tells you something.
Reseat before replacing. DisplayPort connectors in particular have a latch that can look seated while sitting slightly proud, and HDMI plugs work loose over time under the weight of a stiff cable. Push both ends firmly home and retest before assuming the cable has failed.
Cable specification matters at higher resolutions and refresh rates, and it fails in a way that looks like a broken cable rather than an inadequate one. A cable that carried 1080p perfectly can produce nothing at all at 4K or at 144 Hz, and cheap or very long runs are the usual offenders. If the monitor works at a lower resolution and not a higher one, that is a cable or bandwidth limit rather than a fault.
4. Is the computer outputting anything at all?
Establish whether the computer is running before troubleshooting the display path. Listen for fans and drive activity, watch for keyboard lights responding to Caps Lock, and check whether the machine responds to a power button press. A computer that is not posting will produce No Signal on a perfectly good monitor and cable, and that is a different problem entirely.
If it is running, force the output. On Windows, pressing the Windows key with P opens the display options — Microsoft's guidance is to make sure Extend is selected, and cycling through the options blindly with the keyboard often brings a screen back. Windows key, Ctrl, Shift and B together resets the graphics driver, which Microsoft documents for exactly this class of problem and which is worth trying when a setup that was working has suddenly stopped.
Test the monitor on a different computer, or the computer on a different monitor or a TV. Microsoft lists testing the monitor with another system for good reason: it is the single most decisive test available. A monitor that works on a laptop has cleared itself and the fault is the original computer or its cable; a computer that produces no output on two different displays has a graphics problem rather than a display one.
5. When it worked until something changed
A setup that worked and stopped usually has a specific trigger, and identifying it is faster than working through everything. A driver update, a Windows update, a resolution or refresh rate change, a new cable, or a machine that was moved are the usual candidates. Deal with the most recent change first.
An unsupported resolution or refresh rate is a common and confusing one, because the computer is outputting correctly and the monitor cannot display what it is being sent. It typically follows a change made in a game or in the graphics control panel. Boot Windows into Safe Mode, which forces a basic resolution, and set something conservative before restarting normally.
For driver problems, Microsoft's route is Device Manager: expand Display adapters, right-click the adapter, choose Update driver and then Search automatically. If the fault started immediately after a driver update, rolling that driver back from the same properties dialog is the more targeted fix and preserves everything else.
If you can see the BIOS or boot logo and the screen goes blank as Windows loads, that is a driver or resolution problem rather than a hardware one — the monitor and cable are demonstrably working up to that point.
6. When it is hardware, and what to tell support
The evidence for a failed monitor is specific: no on-screen menu, no self-test pattern with the cable removed, and no power light, on a known-good outlet and power cable. That is a monitor fault. Anything short of it — a menu that appears, or a self-test that runs — means the monitor works and the fault is elsewhere.
The evidence for a graphics fault is equally specific: no output from the computer on two different monitors, using two different cables, with the cable in the graphics card's own port. On a desktop, a useful extra test is to remove the graphics card and connect to the motherboard's output, which usually becomes active once no card is fitted; a picture that appears then points firmly at the card.
When you contact support, give them the tests rather than the symptom. Say whether the monitor's own menu or self-test appears, whether the cable is in the graphics card or the motherboard, whether a second cable and a second port behaved the same, whether the monitor works on another computer, and whether the problem began after a specific change. Those five answers separate a monitor from a cable from a port from a graphics card.
Frequently asked questions
Why does my monitor say No Signal?
The message proves the monitor is working — it needs power and a functioning panel to display anything. The fault is between the computer's video output and the monitor. On a desktop with a graphics card, check the cable is in the card's own port rather than the motherboard's, which is usually inactive when a card is fitted and is the single most common cause.
Should the cable go in the motherboard or the graphics card?
The graphics card, on any desktop that has one. Its outputs sit lower on the back of the case, separate from the USB and network ports. Most systems disable the motherboard's video outputs when a card is installed, so a cable plugged in there gives a permanent No Signal even though everything is working.
How do I know if my monitor is broken or my PC is?
Press the monitor's menu button. If its on-screen menu appears, the monitor is fine — that menu is generated internally with no input from the computer. Most monitors also have a self-test that runs with the video cable unplugged. If neither appears and there's no power light on a known-good outlet, the monitor is the fault.
What does an orange power light on my monitor mean?
That it's awake and waiting for video — standby, not a fault. It's the same state as an explicit No Signal message, so troubleshoot the signal path rather than the monitor's power. A monitor with no light at all on a working outlet is the case that points at the monitor itself.
My screen goes blank when Windows loads but I can see the boot logo. Why?
That's a driver or resolution problem, not hardware — the monitor and cable are demonstrably working up to that point. Boot into Safe Mode, which forces a basic resolution, then set something conservative. If it started right after a driver update, roll that driver back in Device Manager rather than reinstalling.
Can a cable cause No Signal even though it looks fine?
Yes, and specification matters as much as damage. A cable that carried 1080p perfectly can produce nothing at 4K or at a high refresh rate, and long or cheap runs are the usual offenders. If the monitor works at a lower resolution and not a higher one, that's a bandwidth limit rather than a broken cable.
Sources and review notes
Checked on . Compiled by Glitchary from Microsoft, Dell and HP support documentation. Monitor menu names, self-test behaviour and power-light colours vary by manufacturer — check the manual for your model. Guidance on motherboard versus graphics card outputs reflects how most desktop systems behave rather than a single vendor’s documentation, and a few systems do run both. Glitchary is independent of Microsoft, Dell, HP and the other manufacturers named here.