Computer Won't Turn On - Complete Troubleshooting Guide

You press the power button and nothing happens. No lights, no sounds, no signs of life. Before assuming the worst and buying a new computer, work through these troubleshooting steps.

At SnapFixRepairs in Oldham, "won't turn on" is our most common repair request. Often, simple fixes solve the problem. Here's the complete guide.

Different Types of "Won't Turn On"

Completely Dead - No Lights or Sounds

Absolutely nothing happens when you press power button. No LED lights anywhere, no fan sounds, total silence.

This suggests power supply, motherboard, or power button issues.

Powers On But No Display

Fans spin, lights illuminate, sounds normal, but monitor shows nothing.

This suggests graphics, cable, or monitor problems rather than complete power failure.

Powers On Then Off Immediately

Computer starts, fans spin briefly (2-3 seconds), then shuts down. Might cycle repeatedly.

This suggests overheating protection, power supply issues, or hardware shorts.

Beeping Sounds

Power turns on, beeping sounds emit, but nothing else happens.

Beep codes indicate specific hardware problems (RAM, graphics, motherboard).

Identify which scenario matches your situation for targeted troubleshooting.

Completely Dead Computer - No Response

Step 1: Check Power Source

Seems obvious but eliminates common oversights:

Test the wall socket: Plug something else in (lamp, phone charger). Verify the socket provides power.

Check power cable: Ensure power cable is firmly seated at both computer and wall.

Try different power cable if available (standard PC power cables are interchangeable).

Power strip issues: If using power strip, verify it's switched on.

Try plugging computer directly into wall socket, bypassing power strip.

Power strips fail. The switch might be on, but internal fuses blow.

Step 2: Check Power Supply Switch

Most desktop power supplies have a switch on the back (near where power cable connects).

This switch should be in "I" or "—" position (on), not "O" position (off).

Easy to accidentally switch off when moving computers or plugging things in.

Step 3: Check Voltage Switch (If Present)

Some power supplies have a red voltage switch (115V/230V).

In the UK, this should be set to 230V.

If set to 115V, computer won't work. Warning: Switching from 115V to 230V while plugged in can damage components. Unplug first, switch, then plug in.

Not all power supplies have this switch - many are auto-switching.

Step 4: Disconnect Everything

Unplug all unnecessary devices:

  • USB devices
  • Printers
  • External drives
  • Extra monitors
  • Headphones

Leave only power cable, monitor, keyboard, and mouse connected.

Faulty USB devices can prevent startup. Disconnecting isolates the problem.

Try powering on with minimal connections.

Step 5: Try Different Power Outlet

Plug computer into different room's outlet.

Some homes have tripped breakers affecting specific outlets.

Verify computer works on completely different electrical circuit.

Step 6: Discharge Residual Power

Residual electrical charge sometimes prevents startup.

Discharge process:

  1. Unplug computer from wall
  2. Hold power button for 30 seconds
  3. Release button, wait 30 seconds
  4. Plug back in
  5. Try powering on

This clears residual charge and often solves mysterious "won't start" issues.

Step 7: Check Power Button Connection

For confident users who can open the computer:

Power button is just a switch. The actual power electronics are on the motherboard.

Inside the computer:

  1. Open case
  2. Find small cable from power button to motherboard (labeled "PWR_SW" or similar)
  3. Ensure it's firmly connected
  4. Try reseating it

Loose power button connection prevents startup but is simple fix.

Advanced: Bypass power button by briefly touching a screwdriver across the two power switch pins on motherboard. If computer starts, power button itself is faulty.

Step 8: Test Power Supply

Paperclip test (described in our Power Supply Failures post):

This tests if PSU works independently.

If PSU fan doesn't spin during paperclip test, PSU is dead and needs replacement.

If PSU passes paperclip test but computer still won't start, problem is elsewhere (motherboard, CPU, RAM).

Powers On But No Display

Step 1: Check Monitor Power

Verify monitor is on (power light should be illuminated).

Check monitor's power cable and switch.

Step 2: Check Monitor Input

Press menu/input button on monitor. Verify it's set to correct input (HDMI, DisplayPort, etc.).

Monitors with multiple inputs sometimes switch randomly.

Step 3: Check Video Cable

Ensure video cable is firmly connected at both monitor and computer ends.

Try different cable if available.

Video cables fail, especially cheap ones.

Step 4: Check Video Cable Location

Critical mistake: Plugging monitor into motherboard video ports instead of graphics card.

If you have dedicated graphics card, monitor MUST connect to graphics card ports (lower on back of computer).

Motherboard ports (higher up) won't work with dedicated graphics installed.

Step 5: Try Different Monitor/TV

Connect computer to different display device.

This identifies if monitor is faulty or computer isn't outputting video.

Try TV with HDMI cable if no spare monitor available.

Step 6: Reseat Graphics Card

For confident users:

  1. Power off and unplug computer
  2. Open case
  3. Remove graphics card (unscrew bracket, unplug power, press PCIe slot clip)
  4. Firmly reinstall graphics card
  5. Reconnect power cables
  6. Try booting

Loose graphics cards cause no display issues.

Step 7: Try Integrated Graphics (If Available)

If you have integrated graphics (video ports on motherboard), temporarily remove graphics card and connect monitor to motherboard.

If display works, graphics card is faulty.

If still no display, problem is elsewhere.

Step 8: Check RAM

Missing or faulty RAM prevents boot and display.

Reseat RAM:

  1. Power off and unplug
  2. Open case
  3. Press clips at RAM ends
  4. Remove RAM completely
  5. Firmly reinstall (should click into place)

If you have multiple RAM sticks, try one stick at a time in different slots.

Faulty RAM or loose RAM causes no display.

Powers On Then Off Immediately

Step 1: Check for Overheating

If computer hasn't been cleaned in years, massive dust buildup causes instant overheating protection shutdowns.

Open case and check for dust accumulation.

Use compressed air to clean thoroughly (especially CPU heatsink).

Step 2: Check CPU Cooler Connection

Ensure CPU cooler fan is plugged into motherboard.

Motherboards often won't boot if CPU fan isn't detected (prevents CPU damage).

Step 3: Check for Shorts

Metal objects touching motherboard cause short circuits.

Check for:

  • Loose screws inside case
  • Motherboard touching case metal (should only contact standoffs)
  • Cables pinched or damaged

Remove case completely and try booting with computer lying flat on non-conductive surface.

Step 4: Check RAM

Try booting with one RAM stick at a time.

Faulty RAM can cause instant shutdowns.

Step 5: Disconnect Non-Essential Components

Remove everything except:

  • CPU and cooler
  • One RAM stick
  • Power connections

Add components back one at a time to identify what causes shutdown.

Beeping Sounds

Beep codes indicate specific hardware failures.

Common beep patterns:

One short beep:

  • Normal startup (not an error)

Continuous beeping:

  • RAM not detected or faulty

Three beeps:

  • RAM problem

One long, two short beeps:

  • Graphics card problem

One long, three short beeps:

  • Graphics card problem

Repeating long beeps:

  • RAM issue

Check your motherboard manual for specific beep code meanings (varies by manufacturer).

Troubleshooting beeps:

Focus on RAM first (most common):

  • Reseat RAM
  • Try one stick at a time
  • Try different RAM slots

Then check graphics card:

  • Reseat graphics card
  • Check power connectors to graphics card

When Professional Help Is Needed

After Trying Everything

You've worked through all steps, problem persists.

Professional diagnostic tools identify exact failure points.

No Confidence Opening Computer

You're not comfortable opening case or handling components.

Professional service prevents accidental damage from inexperienced handling.

Suspected Component Failure

Testing identified likely failed component (PSU, motherboard, RAM, CPU).

Professional confirmation prevents buying wrong replacement parts.

Warranty Concerns

Opening computer yourself might void warranties.

Let professionals handle warranty-covered computers.

SnapFixRepairs Diagnostic Services

Free Initial Assessment

Bring computer to our Oldham workshop. We provide free initial assessment explaining problem category.

Professional Diagnosis: £40-£60

Includes:

  • Complete hardware testing
  • Exact problem identification
  • Repair cost estimate
  • No-obligation quote

Diagnosis fee often waived if you proceed with repairs.

Common "Won't Turn On" Repairs:

Power supply replacement: £80-£150 Motherboard replacement: £120-£300 RAM replacement: £50-£120 Graphics card replacement: £150-£400 Simple fixes (reseating, cleaning): £40-£80

Same-Day Service Often Available

Many "won't turn on" problems fix quickly. Drop off morning, pick up afternoon.

More complex repairs requiring parts orders take 2-4 days.

Honest Assessments

If repair costs approach new computer prices, we'll tell you.

For very old computers with multiple failures, replacement often makes more sense economically.

We profit more from new computer sales than repairs. When we recommend repairs, it's because they're genuinely worthwhile.

Prevention Tips

Use Surge Protectors

Quality surge protectors prevent power supply and motherboard damage from electrical spikes.

Replace surge protectors every 3-5 years (protection degrades).

Regular Cleaning

Dust accumulation causes overheating and component stress.

Clean desktop computers every 6-12 months.

Proper Shutdown

Always shut down properly through Windows. Force shutdowns (holding power button) risk file corruption.

Avoid Power Interruptions

Don't unplug computer while running (except emergencies).

For areas with frequent power cuts, consider UPS (uninterruptible power supply).

Handle With Care

When moving computers, handle gently. Avoid impacts that can dislodge internal components.

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