A PC that powers on, spins its fans and lights up, yet sends nothing to the monitor, is one of the most frustrating faults to troubleshoot because so many different components can be the culprit. This guide walks through a logical elimination process — starting with the cheapest and easiest checks — to find whether the problem lies with the cable, the monitor, the graphics card, the RAM, or the motherboard itself.

First Checks: Rule Out the Simple Causes

Before opening the case, work through these quickly:

  1. Confirm the monitor itself is working. Test it with another device (a laptop, or a different PC) if possible, and make sure it's set to the correct input source (HDMI 1, DisplayPort, etc.) via its on-screen menu buttons.
  2. Try a different cable. Video cables fail more often than people expect, especially at the connector pins.
  3. Try a different port. If you have a discrete graphics card, plug into a different output on the card. If you're currently plugged into a motherboard video port, note that this won't work at all if a discrete GPU is installed — the motherboard output is disabled by default in that case (see below).
  4. Check for beep codes. Listen for beeps from the motherboard's onboard speaker (if fitted) as the PC boots — a pattern of beeps is a built-in diagnostic code pointing to a specific failed component. Check your motherboard manual for what the pattern means, as codes differ between BIOS manufacturers (AMI, Award, Phoenix).

Pro tip: If you have a discrete graphics card installed, always test video output from the graphics card's ports first, not the motherboard's built-in video output. Most motherboards automatically disable onboard video when a discrete GPU is detected, so a "faulty" no-display issue is sometimes just a cable plugged into the wrong port.

Checking the Graphics Card

  1. Power off, unplug the PSU, and earth yourself.
  2. Open the case and check the GPU is fully seated in its PCIe slot — press down firmly and evenly along the card until the retention clip clicks.
  3. Confirm all PCIe power connectors (6-pin, 8-pin or 12V-2x6, depending on the card) are firmly connected. A GPU with insufficient power will often fail to output any signal at all, sometimes without any error indication.
  4. If you have access to another graphics card, or can test yours in another PC, this is the fastest way to isolate whether the GPU itself is faulty.
  5. If you don't have a spare GPU, and your CPU has integrated graphics, remove the discrete card entirely, connect the monitor to the motherboard's video output, and boot. If you get a display this way, the discrete GPU is the likely fault.

Checking RAM

Faulty or poorly seated RAM is one of the most common causes of a no-display boot, often accompanied by beep codes.

  1. Power off and remove all RAM sticks.
  2. Clean the gold contacts gently with an eraser if they look tarnished or dusty.
  3. Reseat one stick at a time in the motherboard's first recommended slot (check the manual — usually slot A2), pressing firmly until the retention clips click into place on both sides.
  4. Boot with just that one stick. If you get a display, power off and test each additional stick individually in the same slot, and then in combination, to isolate whether one stick or one slot is faulty.

Warning: Always power off and unplug the PC before touching RAM or expansion cards. Removing or inserting components while powered can damage the motherboard, the component, or both.

Checking the CMOS Battery and BIOS Settings

A depleted CMOS battery or corrupted BIOS settings can occasionally cause a no-display fault, particularly after a power cut or long period unused.

  1. Try resetting the BIOS/CMOS — locate the small round CR2032 battery on the motherboard, remove it for 5 minutes with the PC unplugged, then reinsert it (see our dedicated guide on safely resetting BIOS/CMOS for full steps).
  2. Alternatively, use the motherboard's Clear CMOS jumper or button if fitted, following the manual's instructions.
  3. Boot again and check for display output.

Checking the Motherboard and PSU

If the above steps haven't resolved it, the fault likely sits with the motherboard or PSU itself.

  1. Check the motherboard for onboard diagnostic LEDs (many modern boards have CPU, RAM, GPU and Boot indicator lights near the 24-pin connector) — an illuminated LED points directly to the stage where boot is failing.
  2. Confirm the CPU power connector (4+4 or 8-pin, separate from the 24-pin) is fully connected — a PC can power on fans and lights with this disconnected, but will never post or display anything.
  3. Test with a different, known-good PSU if you have access to one — insufficient or unstable power delivery is a common cause of a system that appears to power on but never completes POST.
  4. If your motherboard has a debug LED display (a two-digit code readout), cross-reference the shown code against the manual's troubleshooting table for a precise diagnosis.

When It's Likely a Deeper Fault

If you've confirmed the monitor, cable, GPU, RAM and CPU power connector are all good, and there's still no display and no beep codes at all, the issue is likely one of:

  • A dead or badly damaged motherboard (particularly after a power surge)
  • A failed CPU (rare, but possible, especially after a botched overclock or physical damage during installation)
  • A short circuit somewhere in the case (a stray screw touching the motherboard, or a standoff in the wrong position)

To check for a case short, remove the motherboard from the case entirely and test it on an anti-static surface (or the motherboard's original box) with only the CPU, one stick of RAM, and the PSU connected — no case, no other components. If it posts this way, a case short was the cause; carefully recheck standoff placement when refitting.

When to call a professional: If you've methodically eliminated cables, monitor, GPU, RAM, CMOS and a case short, and still have no display or beep codes, this points to a motherboard or CPU fault that typically requires either replacement parts to test with or specialist diagnostic equipment. At this stage, a professional repair service can often confirm the exact failed component faster and more cheaply than continuing to buy replacement parts speculatively.

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