Monitor Says 'No Signal'? Here's What to Check
You press the power button, hear the fans spin up, but your monitor just says "No Signal" and goes back to sleep. Or maybe the screen stays black entirely. This is one of the most common repair shop walk-ins, and most of the time the fix is simple.
Check 1: The Cable
Start here. Seriously. A loose or wrong cable is the cause 40% of the time.
- Unplug and replug the video cable at both ends (monitor and computer)
- Make sure you're plugged into the graphics card, not the motherboard (the ports next to the USB ports on the back are usually the motherboard — the ones lower down, near the bottom of the case, are the graphics card)
- Try a different cable. HDMI cables go bad more often than you'd think
- Try a different port on the graphics card if there are multiple
Check 2: The Input Source
Your monitor might be looking at the wrong input:
- Press the Input/Source button on the monitor
- Cycle through HDMI 1, HDMI 2, DisplayPort, VGA, DVI until you find the right one
- Some monitors auto-detect, but many don't — especially when you switch cables
Check 3: Is the Computer Actually On?
Sounds obvious, but "fans spinning" doesn't mean "computer is booting":
- Do you see keyboard lights (Caps Lock, Num Lock)? If not, the PC may not be POSTing
- Does the hard drive/SSD light blink? Steady blinking = working. No activity = stuck
- Listen for beep codes — a series of beeps from the motherboard speaker means a hardware failure (RAM, CPU, GPU)
Check 4: RAM Reseat
If the computer powers on but there's no display output at all (no BIOS screen, no manufacturer logo), a loose RAM stick is a prime suspect:
- Power off and unplug the computer
- Open the case
- Find the RAM sticks (long thin boards, usually near the CPU)
- Push down the clips on each end, pull the RAM out
- Reseat them firmly until the clips click
- Power on and check
This alone fixes about 20% of "no signal" problems, especially after the computer was moved or bumped.
Check 5: GPU Issues
If you have a discrete graphics card:
- Reseat it: Push it firmly into the PCIe slot until it clicks
- Check power cables: Most GPUs need 6-pin or 8-pin power connectors from the power supply. If one is loose, the GPU won't output video
- Test without it: Remove the GPU entirely and plug the monitor into the motherboard. If you get video, the GPU may be dead
Check 6: CMOS Reset
If something changed in BIOS settings (wrong display output, bad overclock), resetting CMOS clears everything back to factory:
- Unplug the computer
- Find the CMOS battery (a silver coin-cell battery on the motherboard)
- Remove it for 30 seconds, then put it back
- Power on — BIOS settings are now default
When It's a Real Hardware Problem
Most "no signal" problems are cables, inputs, or loose components. If you've checked everything above and it's still blank, bring it in — we'll diagnose it for free.