That blank screen with a floating “no signal” message is a modern headache that stops work, play, and everything in between. You press the power button, hear the fans whirl, but your monitor remains stubbornly dark, insisting it sees nothing from your computer. This moment sparks instant frustration and a flood of worries about broken parts and repair bills. Before you despair, understand this critical point: “no signal” is a common symptom, not a single problem, and it is almost always solvable with a calm and systematic approach.
This guide is built to be your trusted companion through that process. We will move beyond random checklists and explain the simple “why” behind every step. You will learn how a video signal travels from your processor to your pixels, where it can get lost, and how to find the break. Whether you are a first-time builder or someone whose faithful PC just stopped talking to the monitor, we provide a clear path from the simplest five-minute checks to more advanced hardware diagnostics. The core question we answer is precisely why does monitor say no signal, and we do so by giving you the framework to diagnose it yourself.
What “No Signal” Really Means: The Video Signal Chain
To fix the “no signal” error, you must first understand what it is telling you. Your monitor is not complaining about a lack of picture; it is reporting a complete absence of an active video signal from the source you have selected. Imagine the signal as a letter that must travel from the computer’s processor to the monitor’s screen. For the letter to arrive, every step of the journey must be completed successfully. This journey is the video signal chain.
The chain has several critical links that must be connected and functioning. The chain begins with your computer’s software instructions and basic input/output system, which tell the graphics processor to start creating a picture. This graphics processor can be built into your computer’s main processor, called integrated graphics, or it can be a separate card plugged into the motherboard, called a discrete graphics card. The signal then travels out through a physical video port on the back of your computer.
From that port, a cable carries the signal to a corresponding port on your monitor. The monitor’s own internal logic board then receives this signal, processes it, and finally instructs the screen to light up the correct pixels. A failure at any single link—whether it is a software setting, a loose cable, a faulty port, or a powered-off component—will break the entire chain. The monitor, waiting at the end, sees nothing and displays the “no signal” message. Understanding this flow turns troubleshooting from a guessing game into a logical process of checking each link in order.
A crucial and common mistake involves the first part of this chain. If your computer has a separate graphics card installed, the monitor must be connected to a video port on that card. Plugging the cable into the video ports on the motherboard, which are for the integrated graphics, creates an immediate break in the chain because the discrete card is now the primary graphics source. The signal never reaches the motherboard ports. Always ensure your monitor cable is plugged into the correct output on your computer’s case.
Your First 5-Minute Checklist: Rule Out the Simple Stuff
Before you consider opening your computer case or worrying about expensive parts, always start here. These steps address the most frequent and easily fixed causes of a “no signal” error. They require no tools, no technical disassembly, and can solve the problem in moments. Follow this priority order to quickly eliminate the obvious.
First, confirm your monitor is actually on and receiving power. This sounds trivial, but it is a common oversight. Look for a power indicator light on the monitor itself. If it is off, check that the power cable is firmly plugged into both the monitor and the wall outlet or power strip. Try pressing the monitor’s physical power button, not just the keyboard shortcut, to wake it from a deep sleep mode.
Second, check the monitor’s input or source selection. Modern monitors often have multiple video ports, like HDMI, DisplayPort, and VGA. Your monitor might be physically connected to your PC but looking for a signal on the wrong input. Use the buttons on the monitor to open its on-screen menu and navigate to the input or source selection. Cycle through the available options until you find the one matching the port your cable is using. You might see the picture appear instantly.
Third, inspect the video cable connections at both ends. Over time, cables can work themselves loose. Firmly push the cable connector into the port on your computer’s graphics output and then into the port on your monitor. Ensure it is seated completely and that any securing screws, like those on a VGA or DVI cable, are tightened. Look for any obvious physical damage to the cable, like bent pins or severe kinks.
Fourth, try a different video cable if you have one available. Cables can fail internally without showing external damage. A different HDMI, DisplayPort, or other cable can immediately prove whether your current cable is the broken link in the chain. This is a very common fix.
Fifth, test your monitor with another known-working device. Connect your monitor to a different source, like a game console, laptop, or another computer. If the monitor works fine with the other device, you have confirmed the monitor is not the problem and the issue lies with your original computer. If the monitor still shows “no signal” with a different device, the monitor itself or its power supply may be faulty.
Why Does Monitor Say No Signal? Systematic Diagnosis to Isolate the Fault
If the quick checklist did not restore your signal, the problem lies deeper within your computer system. Now, you must become a detective, systematically testing each link in the video signal chain we discussed earlier. The goal is to isolate which component is causing the failure. This process requires a bit more effort but follows a clear, logical path. We will use simple tests and observations to narrow down the culprit without immediately assuming the worst.
If Your PC Has Onboard Graphics
This is a powerful diagnostic step for computers with a processor that has integrated graphics. If your motherboard has video output ports, you can test whether the problem is with your discrete graphics card. First, completely power down your computer and disconnect the video cable from your discrete graphics card. Then, plug the cable directly into one of the video ports on the motherboard. Turn the computer back on.
If the monitor now displays a signal and you can boot into Windows, it strongly indicates an issue with your discrete graphics card, its connection, or its power supply. The core computer system—the processor, memory, and motherboard—is working correctly. If you still get “no signal” even when connected to the motherboard, the problem likely lies with one of those core components, the motherboard’s own video output, or a deeper system configuration issue.
Listening for POST Beep Codes
When you press the power button, your computer performs a Power-On Self-Test, or POST. This is a series of checks the motherboard runs to ensure critical hardware is present and functioning. Many motherboards have a small speaker that will emit a series of beeps if it encounters an error during this test. These beep codes are a direct message from your motherboard about what is wrong.
A single short beep usually means a successful POST and that the core hardware is okay. If you hear a series of beeps—like one long and two short, or repeated short beeps—you need to consult your motherboard’s manual or the manufacturer’s website. These patterns are specific codes that can point directly to a problem with the memory, graphics card, or processor. If your computer is completely silent during boot, with no beeps at all, it could indicate a power supply issue, a motherboard failure, or that the speaker is not connected.
The ‘Keyboard Num Lock’ Test
This is a clever way to check if your computer is actually booting up into the operating system without seeing the screen. Turn on your computer and wait a minute for it to fully boot. Then, press the Num Lock key on your keyboard. Observe the Num Lock indicator light on the keyboard. If the light toggles on and off when you press the key, it means the computer has booted successfully into the operating system and is accepting input.
The video signal is simply not reaching the monitor. This points squarely to a problem in the video portion of the signal chain: the graphics card, the cable, or the monitor settings. If the Num Lock light does not respond at all, it suggests the computer is not completing its boot process. It may be stuck during POST due to a hardware error, meaning the problem is with the core system components like the CPU, RAM, or motherboard.
Diagnostic Flowchart: Your Visual Guide
To visualize this systematic process, follow this logical decision tree. Start at the top: “Monitor shows ‘No Signal.'” First, perform the 5-Minute Checklist. If that fails, check: Does the PC have onboard graphics? If yes, try using them. If you get a signal, the discrete GPU or its connection is faulty. If you get no signal, listen for POST beeps. If you hear error beeps, consult the beep code for RAM, GPU, or CPU faults. If there are no beeps, perform the Keyboard Num Lock test. If Num Lock toggles, the PC is booting—focus on GPU, cable, and monitor. If Num Lock does not toggle, the PC is not booting—focus on core hardware like PSU, RAM, CPU, and motherboard. This flowchart logically eliminates possibilities step by step.
Advanced Hardware & Configuration Checks
When systematic diagnosis points to a problem inside the computer case, it is time for hands-on checks. These steps involve interacting with the internal components. Please proceed with caution and patience. The goal is to reseat connections, clear configuration errors, and ensure everything is receiving proper power. This often resolves issues caused by loose parts or corrupted settings from updates or changes.
Safety First: Disconnect Power and Ground Yourself
Before touching anything inside your computer, you must disconnect all power. Turn off the power switch on the back of the power supply unit, if it has one, and unplug the power cord from the wall. Press the computer’s power button a few times to discharge any remaining electricity stored in the components. To prevent static electricity from damaging sensitive parts, ground yourself by touching a bare metal part of the computer case before handling any components. Working on a clean, non-carpeted surface is also advisable.
Reseating Components
Over time, due to thermal expansion and contraction or minor bumps, expansion cards and memory can become slightly unseated. This breaks their electrical connection to the motherboard. Carefully remove the side panel of your case. Locate your graphics card and your RAM sticks. Unlock the retention clips or screws holding them in place. Gently but firmly remove the graphics card and each RAM module, then reinsert them straight down until the clips click back into place securely. This action re-establishes the critical link in the signal chain between these components and the motherboard.
Inspecting Power Connections
Your graphics card and motherboard require direct power cables from the power supply unit. A loose power cable can cause a component to not function at all. Trace the cables from your power supply. Ensure the wide 24-pin cable is fully plugged into the motherboard. Find the 8-pin or 4-pin CPU power cable near the processor socket and check its connection. For discrete graphics cards, ensure all required PCIe power cables are firmly attached to the card. Some cards need one, two, or even three separate power connectors. A missing or loose cable here is a common reason for a GPU to not initialize, resulting in no signal.
Resetting BIOS to Defaults
The BIOS or UEFI is the low-level software that controls your hardware before Windows loads. An incorrect setting here, like an incompatible memory speed or wrong graphics initialization order, can prevent a signal. To reset it, locate the circular, coin-shaped CMOS battery on your motherboard. With the power disconnected, remove this battery for about five minutes. This clears all custom settings and restores the BIOS to its factory defaults. Alternatively, many motherboards have a “CLR_CMOS” jumper or button; consult your manual for its location. After resetting, reconnect the battery or close the jumper, reassemble, and try booting again.
Updating and Managing Software
Sometimes, the issue originates in the software layer. If you can get a signal using onboard graphics but not your discrete card, boot into Windows using the onboard graphics. Then, visit the website of your graphics card manufacturer to download the latest drivers. Use a driver removal tool to completely uninstall the old drivers, then install the fresh ones. Also, check for BIOS/UEFI updates from your motherboard manufacturer, but only attempt this if you are confident and have a stable power source, as a failed update can brick your motherboard.
Scenario-Specific Troubleshooting
The context in which the “no signal” error appears greatly changes the most likely causes. Applying the general diagnostic framework to your specific situation makes the process more efficient.
For a Brand New PC Build
If you are assembling a PC for the first time and it will not display a signal, focus on assembly errors. Double-check that you installed the motherboard standoffs correctly, preventing a short circuit. Verify that both the 24-pin motherboard power and the 8-pin CPU power cables are securely connected. Ensure your RAM modules are pressed fully into their slots until the side clips snap closed. Confirm that your graphics card is fully seated in its PCIe slot and that all required power cables from the PSU are attached to it. First builds often have a simple, overlooked connection issue.
For a PC That Was Working Yesterday
If your system was functioning perfectly and suddenly displays “no signal,” think about what changed. Did you install a Windows update or new software? A driver conflict could be the cause. Did you add new hardware, like more RAM or a storage drive? A faulty new component or improper installation can disrupt the system. Did you move the computer or desk? The video cable may have been pulled loose. Retrace your recent actions as they often point directly to the source of the problem.
For Intermittent “No Signal” Issues
A problem that comes and goes is often related to heat, power, or physical connections. If the signal disappears under heavy load, like during gaming, your graphics card or CPU may be overheating. Monitor temperatures using software when the system is working. Intermittent failure can also point to a failing power supply unit that cannot deliver stable power consistently. Finally, a slightly loose cable or a failing graphics card that works only when cold can cause random signal loss. Check all connections and consider stress-testing your components.
Frequently Asked Questions
Why does my second monitor say “no signal”?
When a second monitor reports “no signal,” the issue is almost always in the configuration or the physical connection to that specific monitor. First, ensure the cable is securely connected to both the second monitor and a correct video output on your computer. Then, right-click on your Windows desktop and select “Display settings.” Scroll down and click “Detect” to make Windows look for the second display. Confirm that the multiple display setting is set to “Extend these displays” or “Duplicate these displays,” not “Show only on 1.” The monitor itself may also need its input source manually set to the correct port.
Why does my monitor say “no signal” then turn off or go to power saving?
This behavior is a clear sign that your monitor is functioning correctly but is receiving absolutely no active video signal from the computer. The monitor waits, sees nothing, and then enters its normal power-saving mode as if the computer were shut off. This confirms the break is in the signal chain before the monitor. Your computer is likely failing to initialize its graphics hardware during the boot process, so it never sends a signal. Focus your troubleshooting on the computer’s components, particularly the graphics card, motherboard, and power supply, using the systematic diagnosis methods outlined earlier.
I’ve tried everything and get no signal. Is my GPU dead?
While a dead graphics card is a possibility, it is not the only conclusion. Other failures can mimic a dead GPU. A faulty PCIe slot on the motherboard, a severely underpowered or failing power supply unit, or even a malfunctioning central processor can all prevent the graphics system from initializing. The definitive test is to try your graphics card in a known-working computer. If it also fails there, the GPU is likely faulty. Before declaring it dead, ensure you have thoroughly tested with a known-good power supply and tried different PCIe slots if available, as these are more common points of failure.
Solving the “no signal” mystery is a process of elimination, guided by understanding the video signal chain. Start with the simplest external checks before moving inward. Use the symptoms—like beep codes or keyboard lights—to guide your focus. Remember that frustration is normal, but patience and a systematic approach will almost always identify the broken link. Whether it was a loose cable, a monitor setting, or a component that needed reseating, the answer to why does monitor say no signal lies in methodically checking each step of the journey from your computer to your screen. With this guide, you have the map to find it.
