You boot your PC and your monitor flashes "No Signal" — then goes dark. Or maybe it happened out of nowhere mid-session. Either way, something between your computer and your screen broke the conversation, and you need to find out what.
The good news: "no signal" almost always means the connection failed, not that something is destroyed. Nine times out of ten, it's the cable, the input source setting, or the drivers. Work through the steps below in order — most people fix it in under five minutes.
What "No Signal" Actually Means
Your monitor is powered on and working. It's waiting for a video signal from a connected device — and it's not getting one.
Think of it like a phone call where the monitor picked up but can't hear anyone on the other end. The problem is somewhere in the chain: the cable, the port, the graphics card, or the signal settings. The monitor itself is usually fine.
The four most common causes, in order of frequency:
- Wrong input source — the monitor is watching the wrong "channel"
- Loose or faulty cable — the signal isn't getting through
- Bad GPU port or driver — the source isn't outputting properly
- Unsupported resolution/refresh rate — the signal is there but the monitor can't read it
Step-by-Step Fix Guide
Step 1: Check the Input Source on the Monitor
Every monitor has an input selector. On most modern monitors, you'll find a joystick on the back-bottom or a button on the front bezel. Press it, navigate to "Input Source" or "Input Select," and confirm you're on the right one.
If you plugged your cable into HDMI 2 but the monitor is set to HDMI 1 — or DisplayPort when you're on HDMI — the monitor will show no signal even if everything else is perfect.
Step 2: Reseat the Cable at Both Ends
Unplug your HDMI or DisplayPort cable from both the monitor and the PC. Check for bent pins (in HDMI cables especially), then firmly plug both ends back in. Push until it fully seats — you should feel resistance stop.
If your cable has a screw-lock (DisplayPort cables sometimes do), make sure it's engaged. A half-seated DisplayPort cable is a very common culprit.
Step 3: Try a Different Cable
Cables fail more often than people expect, especially HDMI. A damaged inner conductor can carry power but drop the data signal intermittently. Swap in any other cable you have — the one that came with a TV, a spare in a drawer, anything.
Also check that the cable supports your target resolution. A standard "High Speed HDMI" cable handles up to 4K@30Hz. For 4K@144Hz, you need HDMI 2.1 or DisplayPort 1.4. Using the wrong spec cable with a high-end GPU + monitor combination will produce no signal or flickering.
Step 4: Test a Different Port on Your GPU
Most discrete GPUs have two or more HDMI/DisplayPort outputs. If your cable was in HDMI 1, try HDMI 2 or a DisplayPort. If one port is dead (it happens — ports can fail from electrostatic discharge or physical stress), the others may work fine.
If you're running integrated graphics (no discrete GPU), you'll only have the single output on the motherboard's I/O panel. In that case, skip to Step 5.
Step 5: Check Your Resolution and Refresh Rate Settings
This one bites people after a driver update or after connecting to a new monitor. If your PC is outputting a resolution or refresh rate the monitor doesn't support — say, 1440p@165Hz on a monitor that only does 1080p@60Hz — the monitor will show no signal.
To fix it when you can't see anything:
- Boot into Safe Mode (hold Shift when clicking Restart in Windows, or spam F8 at startup). Safe Mode defaults to 800×600 which any monitor supports.
- Once in Safe Mode, go to Display Settings and set resolution to 1920×1080 and refresh rate to 60Hz.
- Restart normally.
Alternatively, if you have a second monitor or a laptop with a built-in screen, use that to change the settings without needing Safe Mode.
Step 6: Update or Roll Back Your GPU Driver
A bad driver update can cause sudden no-signal on ports that worked yesterday. This is especially common after Windows Update installs a display driver automatically.
In Safe Mode or on a second display:
- Open Device Manager (right-click Start → Device Manager)
- Expand Display Adapters
- Right-click your GPU → Properties → Driver tab
- Try "Roll Back Driver" first if it's available. If not, click "Update Driver" → "Search automatically"
For NVIDIA users, DDU (Display Driver Uninstaller) is the gold standard for a clean driver removal and reinstall when rollback doesn't solve the issue.
→ Anker Cable & Surge Protector on Amazon — Anker's cables are reliably rated and reasonably priced.
Step 7: Test the Monitor on a Different PC
This is the isolation test. Grab a laptop, a work computer, a friend's machine — anything with a video output. Plug your monitor in.
- If it works: The monitor is fine. The problem is your PC (GPU, driver, cable port, or settings).
- If it still shows no signal: The monitor itself has a problem — the input board, the panel, or a failed port on the monitor side. Time to check warranty or consider repair.
Specific Scenarios
New Build or New Monitor — Never Worked
Check that your GPU is properly seated in the PCIe slot (lever should click). Confirm you plugged the monitor cable into the GPU's output, not the motherboard's display output (if you have a discrete GPU, you must use the GPU ports, not the ones near the USB ports on the back of your case).
If you're using integrated graphics (no GPU), you'll use the motherboard ports. If your CPU doesn't have integrated graphics (AMD Ryzen 5000 "X" chips, for example), you must have a GPU installed.
Second Monitor Keeps Losing Signal
Intermittent no-signal on a second monitor often means the GPU is pushing the cable bandwidth limit. Try lowering the refresh rate on that monitor (e.g., from 144Hz to 60Hz) to see if it stabilizes. Also check that the cable going to the second monitor is the same quality as the first — people often run premium cables to the main monitor and use an old cable for the secondary.
After Waking from Sleep
Some monitors lose the handshake with a PC after sleep/hibernate. This is a known issue with certain DisplayPort monitors — the monitor powers off completely during sleep, and when the PC wakes, the two can't re-establish the link.
Fix: In Windows Power Settings, set your display to "Never turn off" (let the monitor's own sleep timer handle it). Or switch from DisplayPort to HDMI, which handles power cycling more gracefully on most hardware combinations.
After a Windows Update
Windows Update occasionally installs generic display drivers that override your GPU manufacturer's driver. Boot into Safe Mode, uninstall the generic driver from Device Manager, and reinstall the correct driver from NVIDIA, AMD, or Intel's website directly.
Test Your Monitor for Pixel Issues →When to Suspect the Monitor Itself
The monitor is the least likely culprit — but it does fail. Signs that point to the monitor rather than the PC:
- No signal on all inputs (HDMI and DisplayPort both fail)
- The monitor works with another PC's output
- Physical damage near the port (bent pins, cracked connector)
- Monitor is out of warranty and more than 5 years old
Monitor input board repair is possible but rarely cost-effective for monitors under $300. If your monitor is older and shows no signal regardless of cable, PC, or port, a replacement is usually the pragmatic call.
Quick Diagnostic Summary
| Symptom | Most Likely Cause | Fix |
|---|---|---|
| Never worked on new build | Wrong port (mobo vs GPU) or input source | Use GPU port, check input selector |
| Worked, now suddenly fails | Loose cable, driver update, or bad port | Reseat cable → rollback driver → try different port |
| Flickering then no signal | Dying cable or failing GPU port | Replace cable → test with different port |
| After sleep/wake | DisplayPort power handshake issue | Switch to HDMI or disable display sleep |
| After Windows Update | Generic driver override | Reinstall GPU manufacturer driver |
| Second monitor only | Cable bandwidth or refresh rate too high | Lower refresh rate, upgrade cable |
Frequently Asked Questions
Why does my monitor say no signal?
Usually: wrong input source selected, loose or faulty cable, or a driver issue. Start by pressing the monitor's input/source button and confirming it matches the port your cable is plugged into.
Monitor says no signal but computer is on — what do I do?
Check the input source, reseat the cable, try a different cable. If you recently updated drivers, boot into Safe Mode and roll them back. If nothing works, connect the monitor to a different PC to determine whether the fault is the monitor or the computer.
Can a bad HDMI cable cause no signal?
Yes — it's one of the most common causes. Swap in any other cable you have. Also confirm your cable supports your target resolution (4K@144Hz requires HDMI 2.1 or DisplayPort 1.4).
Why does my second monitor keep losing signal?
Usually insufficient cable bandwidth for the resolution + refresh rate combination. Lower the second monitor's refresh rate to 60Hz and see if it stabilizes. Also check the cable quality — second monitors often get leftover cables that don't support higher specs.