Few things are more alarming than pressing the power button on your desktop and getting nothing at all — no lights, no fans, no beeps. The good news is that a completely dead PC is often caused by something simple and cheap to fix, like a loose cable or a tripped switch, rather than a major component failure. This checklist works through the problem methodically, from the simplest checks to the more involved internal ones, so you can narrow down the cause without guessing.

Step 1: Rule Out the Obvious External Causes

Before opening the case, work through these quick checks — they solve a surprising number of "dead PC" cases.

  1. Check the wall outlet. Plug a different device (like a lamp or phone charger) into the same socket to confirm it's providing power.
  2. Check the power cable itself. Try a different kitchen or monitor power cable, as these are a common, cheap failure point.
  3. Check any extension lead or surge protector. These often have their own power switch or reset button, and can fail silently. Plug the PC directly into the wall to test.
  4. Check the PSU's rear rocker switch. Located on the power supply at the back of the case, confirm it's set to "I" (on), not "O" (off).
  5. Check the PSU voltage switch (rare, mainly on older units). Some PSUs have a 115V/230V selector switch — this should be set to 230V in the UK. Setting it incorrectly can prevent the PSU from working.

Safety warning: If a PSU voltage switch has ever been set to the wrong region, do not power the system on to "test" it — incorrect voltage settings can damage components. Check it visually first with the PC unplugged.

Step 2: Check for Any Signs of Life

With the case closed, press the power button and observe carefully:

  • Nothing at all — no lights, no fan movement, no noise: Points to a power delivery problem — proceed to Step 3.
  • Fans spin briefly then stop: Often indicates the motherboard is cutting power due to a detected fault, commonly a short circuit or component issue — proceed to Step 4.
  • Fans and lights come on and stay on, but no display and no beeps: Suggests power is reaching the system but it isn't completing POST (Power-On Self-Test) — see our companion guide on beep codes and POST errors for the next steps.
  • PC powers on, runs briefly, then shuts off repeatedly: This pattern often points to overheating or a power-related trip — see our guide on diagnosing random shutdowns.

Step 3: No Signs of Life at All

  1. Open the case and check every cable is firmly connected: the 24-pin main motherboard power connector, the 4-pin or 8-pin CPU power connector near the top of the board, and the front-panel power switch connector (a small 2-pin cable, usually labelled PWR_SW, connecting the case's power button to the motherboard).
  2. Test the front panel switch directly. Using a small flathead screwdriver, briefly touch the two pins on the motherboard header the PWR_SW cable normally connects to (consult your motherboard manual for exact pin location). If the PC powers on this way, the case's physical power button or its cable may be faulty.
  3. Check the PSU with a paperclip test. With the PSU unplugged from the motherboard but still plugged into the wall, locate the 24-pin connector, and use a paperclip to bridge the green wire pin to any black (ground) wire pin. If the PSU's fan spins, the PSU itself is likely receiving power and switching on, which helps isolate whether the fault lies with the PSU or elsewhere.

Pro tip: The paperclip test only confirms the PSU can switch on — it doesn't confirm it's delivering correct, stable voltages under load. A PSU tester tool, available cheaply, gives a more reliable readout of each voltage rail.

Step 4: Fans Spin Briefly Then Stop (Possible Short Circuit)

This pattern often means the motherboard's protection circuitry is shutting things down due to a detected fault.

  1. Check for a case standoff short. If the motherboard was recently installed or reseated, an extra brass standoff touching a bare part of the board's underside can cause a short. Reopen the case and visually inspect between the motherboard and the case's back panel.
  2. Remove and reseat the RAM. Faulty or poorly seated RAM can sometimes cause this pattern. Try booting with a single stick, testing each one individually.
  3. Disconnect all non-essential components. Unplug all drives, the graphics card (if you have integrated graphics as a fallback, or can test with a different monitor cable), and any additional case fans or RGB controllers, leaving only the CPU, one stick of RAM, and the cooler connected. Attempt to power on. If it now works, reconnect components one at a time to identify the culprit.
  4. Inspect for visible damage. With the PC unplugged, look for swollen or leaking capacitors on the motherboard (small cylindrical components that should have flat tops, not bulging or crusty ones), burn marks, or a distinct burnt smell, which point to a failed component needing replacement.

Step 5: Testing with Minimal Components

If you've ruled out cables and switches, building the PC down to its bare essentials outside the case (on an anti-static surface, such as its own box) can help isolate the fault:

  1. Place the motherboard on its box or a non-conductive surface.
  2. Connect only the CPU (with cooler), one stick of RAM, the 24-pin and CPU power connectors, and a speaker if you have one for beep codes.
  3. Attempt to power on using the paperclip test on the front-panel header pins.
  4. If it powers on and beeps normally outside the case, the fault likely lies in something case-related — most often a standoff short or a faulty front-panel switch. If it still shows no signs of life, the issue is more likely the PSU, motherboard, CPU, or RAM itself.

Troubleshooting Summary Table (in text form)

  • No lights or fan movement anywhere: Cable, wall socket, PSU switch, or PSU failure.
  • Fans spin briefly then stop: Possible short circuit, faulty RAM, or motherboard protection trip.
  • Everything powers on, no display, no beeps: POST failure — see the beep codes guide.
  • Powers on then shuts off repeatedly: Overheating or power-related shutdown — see the random shutdowns guide.

When to Call a Professional

If the bare-bones test outside the case still shows no signs of life, or you've identified visible damage like a swollen capacitor or burn marks, the fault likely lies with the motherboard, CPU, or PSU itself — components that are difficult to test further without spare known-good parts. A repair technician has access to PSU testers, spare test benches, and replacement parts to quickly isolate which component has failed, which can save you from buying an expensive replacement part that turns out not to be the problem.

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