Computer Won't Turn On Troubleshooter｜Trace the Power Path From the Wall Outlet to the Screen
A yes/no checklist for when a computer shows no sign of life, or the fans spin but the screen stays black. It checks the outlet, the power cable or charger, the computer's power, the inside of the computer and the screen, in that order. It is built to be followed on a phone, with animated pictures of what to check and a 20-second timer for the power-drain step.
💡 About this tool
When a computer won't start, most people assume it's dead. Manufacturer support guides start somewhere else: the outlet, the power cable, and whatever is plugged in. Power comes from the wall, runs through the cable into the computer, drives the parts inside, and finally reaches the screen as a picture. Somewhere along that path it stops. This tool checks each point in turn, starting from the wall.
The first question is what happens when you press the power button. If nothing lights up and no fan moves, power probably isn't reaching the computer. If lights and fans come on but the screen stays black, power is getting in, and the problem is inside the computer or on the display side. If it beeps or stops at the maker's logo, the computer clearly has power, so the tool skips the outlet and cable checks.
The outlet check sounds too basic to matter, but it catches real problems. Dell's guide suggests plugging straight into the wall instead of a power strip or surge protector, and making sure the outlet isn't controlled by a light switch that's turned off. The tool asks you to test the same outlet with a lamp or phone charger first.
The power-drain step is the one that confuses people most. Parts inside a computer store electricity, and some of it stays there after you unplug. Japanese maker Fujitsu explains that an overcurrent or overvoltage can trip a protection circuit and stop the computer from turning on, and that draining the stored charge lets the circuit return to normal. Removing the cable and battery cuts off the supply. Holding the power button then gives the leftover charge somewhere to go. Maker guides put the hold time at roughly 15 to 30 seconds. The tool uses 20, with a countdown ring, but if your model's guide gives a different time, follow it.
Two other checks work without a working screen. Pressing Caps Lock tells you whether the computer is running: the key light is switched by the computer itself, so if it toggles, the machine is alive and the problem is the picture. On a laptop, shining your phone's flashlight at the screen from an angle does something similar. If you can make out a faint image, the laptop is sending a picture and the light behind the screen (the backlight) is what has failed.
The map at the top shows where you are: cyan for the spot being checked, green for parts that work, red for the likely cause. Your answers are saved on this device, and the screen stays awake during the timer on browsers that support it.
🧐 Frequently Asked Questions
Will draining the power delete my files?
No. Draining only empties leftover electricity from the circuits and doesn't touch saved files. Anything you hadn't saved was already lost when the computer shut off.
The fans spin but the screen is black. What does the tool check?
Since the computer has power, it first checks whether the computer is actually running, then moves to the display. On a desktop that means the monitor's power light, the video cable and input setting, a display reset shortcut, then another screen. On a laptop it means brightness and the flashlight test, the shortcut, then an external screen.
It turns on, then cuts out. Should I keep switching it on to test?
No, power it on only once, at the end. A CPU that gets too hot shuts the computer off to protect itself, so if heat is the cause, every start heats it up again. The tool has you do the checks that need no power first (outlet, cables, extra devices, dust, draining the power), then switch it on one time while filming with your phone. You can replay the video to record the beeps.
If it stays on for a little while, check the CPU temperature on the BIOS screen. Liquid-cooler maker NZXT treats 70°C (158°F) or more at idle as a sign of trouble. With an all-in-one liquid cooler, the fans can keep spinning while the pump has stopped, so don't judge by the fans alone.
What does Windows key + Ctrl + Shift + B do?
Microsoft's support page lists it as a way to reset the graphics driver when the screen goes black. If it works, you'll hear a beep or see the screen flicker. It only works on Windows.
My laptop's charging light won't come on.
Chargers can work loose in three places: at the wall, where the cord meets the power brick, and at the laptop. Reseat all three, and if the light still stays off, try another charger, but only one from the same maker that is listed for your model. A charger from another device can have the wrong voltage even when the plug fits, and that can damage the computer or make it overheat. A small phone charger may not deliver enough power to run a laptop. If you continue without trying a second charger, the result screen adds a note that the charger could still be the cause.
Why doesn't the tool ask me to reseat the RAM?
That means opening the case, which carries a risk of electric shock, injury, damage and a voided warranty. The tool sticks to checks you can do without opening anything, narrows down where the problem is, and leaves the rest to a repair service.
What should I tell the repair shop?
At the end, "Notes for the repair shop" lists every step you tried and the result, including any beeps or blinks you recorded. Copy it and pass it on so they don't have to repeat the same checks. Add the model name, when it started and what happened just before.
What if it starts working halfway through?
Steps where you try something, such as reseating a cable or draining leftover power, have an "It works now" option. Choosing it records what you did right before the fix, which is useful if the problem comes back.
📚 What Startup Beeps Are Telling You
Right after you press the power button, the computer runs a quick check of its own hardware called the power-on self-test, or POST. When it finds a problem, many computers report it with a pattern of beeps or blinking lights. On many machines a single short beep simply means the test passed.
The catch is that the patterns aren't universal. They depend on the firmware the maker used, so the same sequence can mean different things on an AMI-based board and a Phoenix-based one. Dell's own guide says to count the beeps or blinks and look them up in your model's manual. That's why this tool doesn't guess what a code means. You tap short or long in the order you hear them, and the pattern goes into your notes, ready to search with your model name or hand to a technician.