Computer Won't Turn On: How to Tell Power From Hardware

What "won't turn on" usually means

Three very different failures get described the same way at our counter. Sorting them out first saves time and money, because each one points at a different part of the machine.

• Completely dead — no lights, no fan noise, nothing at all when the button is pressed.
• Powers up but nothing on screen — fans spin, lights come on, the display stays black.
• Starts and stops — it powers on for a second or two, then shuts off, sometimes repeatedly.

Which of those three you have is the single most useful thing you can tell a technician, so pay attention to it before you start changing anything.

Possible causes

Before you open anything

Safe things you can try

1. 1

   Prove the outlet works

   Plug a lamp or phone charger into the same outlet. Skip the surge strip and go straight to the wall — failed strips are common and cost nothing to rule out.

2. 2

   Check the power supply switch

   On a desktop, the rocker switch beside the cable entry on the back must be set to I, not O.

3. 3

   Drain residual power

   Unplug the machine, hold the power button for 20 seconds, then plug it back in and try again. On a laptop, remove the battery first if it comes out easily.

4. 4

   Reduce it to essentials

   Unplug printers, hubs, external drives and extra monitors. A shorted USB device can stop a machine from starting.

5. 5

   Confirm the monitor if fans spin

   Check the monitor's own power light and input source, and if the desktop has a graphics card make sure the cable is in the card's port rather than the motherboard's.

What each result may indicate

• Works on a different outlet — the original outlet or surge strip is the problem, not the computer.
• Still completely dead on a known-good outlet — most often the power supply on a desktop, or the charger or charge port on a laptop.
• Fans and lights but no display — usually memory, graphics or motherboard, and it needs proper testing to say which.
• Powers on and immediately off — treat this as a hardware fault and stop; repeated attempts can make a shorting board worse.

When to stop troubleshooting

Stop if you smell burning, see scorch marks, hear repeated clicking from a hard drive, or if the machine has recently had liquid spilled in it. Stop as well if the only remaining steps involve swapping internal parts you'd have to buy on a guess.

When professional diagnosis makes sense

Once outlets, cables and accessories are ruled out, the remaining causes are all inside the machine and need known-good parts to test against. That is a bench job, and it is the reason we keep tested power supplies and memory on hand rather than guessing at parts.

You can bring it to the counter at our Bellevue shop and talk it through with us first — that part is free, and it is often enough to tell you whether the repair is worth doing.