My Lenovo IdeaPad C340's display has become so dim that I need to shine my phone's flashlight on it to read anything. I can still faintly see the picture, and I know where the brightness control is, but changing it—even setting it to maximum—does nothing. What should I test to determine whether this is a software issue, a bad cable, or a failed backlight?
3 Answers
Check whether the screen is equally dim inside the BIOS. If it is dark there too, the problem is almost certainly hardware, such as a failed backlight, display cable, or panel. If the BIOS looks normal, try Safe Mode or reinstalling the graphics and display drivers, since the operating system may be causing it.
Since the image is still visible when you shine a light on it, the LCD is probably producing an image but its LED backlight is not working. A loose display cable is possible, but a failed backlight or panel is more likely. The laptop may need a panel replacement, and it is worth having a shop check it before attempting the repair yourself.
I would avoid taking it apart unless you are comfortable working with small connectors and laptop hinges. A technician can usually tell whether it is the cable or panel fairly quickly.
If you cannot use the built-in screen, an HDMI monitor or TV can serve as a temporary solution. Most laptops will send the picture to it automatically after startup, or you can use the display-switch keyboard shortcut. A portable HDMI monitor is another option, but repairing the laptop may be cheaper depending on the diagnosis.
A replacement panel or backlight can vary a lot in price. Before buying anything, try connecting an external monitor or television if you can, and get a repair-shop estimate. Replacing the panel yourself can be difficult without the right tools.