A monitor showing “no signal” means it’s receiving power and functioning, but isn’t detecting any video output from the connected device at all. This is different from a garbled or corrupted image, and points specifically toward a connection issue, wrong input source, or a PC that isn’t actually producing video output for a deeper reason.
- No signal means the monitor works but isn’t receiving any video data.
- Wrong input source selection is one of the most common, simplest causes.
- A loose or faulty cable is the next most common cause to rule out.
- If the PC itself isn’t posting, no signal is really a symptom of that deeper issue.
Step 1: Check the Input Source
Most monitors have multiple inputs (HDMI, DisplayPort, VGA, DVI), and the monitor’s onscreen menu must be set to the one your PC is actually connected to. This is the single most common cause of a no signal message, especially after switching cables or connecting a second device.
Step 2: Check the Cable Connection
- Confirm the cable is fully seated at both the monitor and PC ends
- Try a different cable entirely, since a damaged cable can produce no signal even when everything else is correct
- Try a different port on both the monitor and the PC, if additional ports are available
Step 3: Confirm You’re Plugged Into the GPU, Not the Motherboard
If you have a dedicated graphics card, the cable must connect to the GPU specifically, not the motherboard’s built-in video output, following the same distinction covered in PC turns on but no display.
Step 4: Test With a Different Monitor or Device
If possible, connect a different monitor to the same PC, or connect your current monitor to a different device, to isolate whether the monitor or the PC’s output is the actual source of the problem.
Step 5: Check If the PC Is Actually Posting
If no combination of cables, ports, or input sources resolves the no signal message, the underlying issue may be that the PC itself isn’t producing any video output at all, following the deeper diagnostic steps in PC turns on but no display. In this case, “no signal” is a symptom of a boot-level issue, not a display-specific one.
Multiple Monitor Considerations
If only one of multiple connected monitors shows no signal, check that display’s specific cable and input source individually, since a multi-monitor setup issue often isolates to just one connection rather than the whole system.
Does a Sleeping PC Cause This?
A PC in sleep mode can sometimes cause a temporarily blank or no signal display that resolves once the system wakes, which is normal and not a fault. Try moving the mouse or pressing a key before assuming a deeper issue.
Quick check first: before any deeper troubleshooting, cycle through your monitor’s input sources manually using its onscreen menu, since this resolves a surprising number of no signal cases in seconds.
See also PC turns on but no display and community troubleshooting on r/buildapc, plus guidance from Tom’s Hardware and iFixit.
Frequently Asked Questions
What does “no signal” actually mean on a monitor?
It means the monitor is powered and working but isn’t receiving any video output from the connected device at all.
What’s the most common cause of a no signal message?
An incorrect input source selection on the monitor itself, easily fixed through the monitor’s onscreen menu.
Could no signal mean my PC isn’t actually working?
Yes, if cable and input checks don’t resolve it, the PC itself may not be posting or producing video output at a deeper level.
Why does only one of my two monitors show no signal?
Check that specific monitor’s cable and input source individually, since multi-monitor issues often isolate to a single connection.
