Monitor Says 'No Signal'? Troubleshooting Steps
Your computer's on, the fans are spinning, but the monitor just says "No Signal" — or sits stubbornly black. It looks like catastrophe; it usually isn't. In our workshop, "no signal" cases turn out to be the cable, the input setting or the monitor far more often than a dead PC. Work through these checks in order — most take under a minute — and you'll either fix it on the spot or know exactly what's really at fault.
Check the obvious first
- The cable. Reseat it firmly at both ends, and try a different cable if you have one — HDMI and DisplayPort cables fail surprisingly often, and a half-seated plug is the single most common cause of the lot. If the picture flickers when you wiggle the cable, you've found your culprit.
- The input source. Make sure the monitor is set to the input you're actually plugged into (HDMI 1, HDMI 2, DisplayPort…). Use the monitor's menu button to cycle through inputs — monitors switched to an empty input are a daily occurrence.
- Power and standby. Confirm the monitor itself is on (does its menu appear when you press the button?) and not asleep. A monitor whose menu won't even appear has a power problem of its own, nothing to do with the PC.
Narrow down the culprit
- Swap test. Try the monitor with another device — a laptop, a games console — or try your PC with another monitor or the living-room TV. Two minutes of swapping instantly tells you which side of the cable the fault lives on.
- The right port. On desktops with a dedicated graphics card, make sure the cable is in the graphics card's ports (usually lower down, on the card) and not the motherboard's video output above them. Plugging into the motherboard when a graphics card is fitted is a classic mix-up — the motherboard output is usually disabled, so you get a perfectly healthy PC and a blank screen.
- Is it actually booting? Listen and look: fans spinning up, keyboard lights, a beep pattern, disk activity. A PC that's completely dead is a different problem — see our won't-turn-on checklist.
Logo appears, then black? Read that clue
If you briefly see the manufacturer or BIOS logo and then lose the signal as the system loads, that's genuinely useful information: the hardware chain — PC, cable, monitor — all works, and the problem is software. It's usually a graphics driver that's failed or a display setting (like a refresh rate the monitor can't handle) applied by mistake. Boot into Safe Mode, which uses a basic display driver, and reinstall or roll back the graphics driver from there. No picture at all, even at the logo, points back to hardware — cable, monitor, or the graphics output itself.
Multiple monitors and adapters: the extra suspects
Running two screens, or using an adapter (HDMI-to-DisplayPort, USB-C docks and dongles)? These add their own failure points. Adapters die quietly and are a frequent cause of one monitor working while the other doesn't; docks can lose their video function while still charging happily. Test with a direct cable wherever possible, and on Windows press Windows key + P to check the display mode isn't set to an output that skips the screen you're staring at. A "missing" second monitor is often just a projection-mode setting.
When it points to the PC
If the monitor and cable are proven good on another device but the PC still sends nothing, the fault is inside the machine — commonly loose or failed memory, a graphics card that has died or unseated, or a motherboard issue. Reseating the RAM and the graphics card fixes a fair share of these, but if you're not comfortable working inside the case, this is the point to stop: further poking without knowing the cause can turn a small fault into a bigger one. A machine that beeps in a repeating pattern at power-on is telling you a diagnostic code — note the pattern, as it identifies the faulty component.
We'll find it fast
Our computer repair team diagnoses display and no-signal faults every week — from cables and monitors to graphics cards, memory and board-level faults — and gives you a clear quote before any work. If it's a flickering screen rather than a blank one, we've a guide for that too.