Why won't an HP all-in-one PC turn on when the rear light is lit?
Answer
A rear power light with no display usually means the adapter is getting power but the PC is stuck, not fully switching on, or the screen backlight failed. Do a full power drain, try the HP logo key combinations for hard power, then use warranty support if it still stays black.
Before you start: stop right away if…
- Use the correct HP adapter only. An underpowered third-party brick can leave a rear light on without starting the system.
Follow these steps
Perform a full power drain
Shut the PC off if possible, unplug the power cord from the wall and from the PC, disconnect all USB devices, then press and hold the power button for 15–20 seconds. Wait one minute.
You should see: Residual power is cleared and the rear light goes off while unplugged.
Reconnect and attempt startup
Plug power directly into a wall outlet (not a faulty strip), reconnect only keyboard/mouse if needed, and press the power button once. Watch for logo, fan activity, or sound.
You should see: The HP logo appears, or you can clearly tell that nothing boots despite power being present.
Test display clues
Shine a flashlight at an angle on the screen while powering on. If a very faint image is visible, the backlight may have failed rather than the whole PC.
You should see: You either see a faint image (display issue) or no image at all (broader power/board issue).
Start an HP warranty case
With the model and serial number from the rear label, contact HP support or the seller for warranty repair/replacement. Do not open the chassis yourself while under warranty.
You should see: HP or the retailer opens a service or replacement order.
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Extra tips
What to look for: Whether any HP logo, fan spin, or beep occurs after pressing power, and whether the rear LED changes when the power button is held.
Before you change anything: Confirm the exact HP model from the rear service label. Use only the original HP power adapter if available. Since the PC is under warranty, avoid opening the case. Disconnect nonessential USB devices before testing.
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