1. Make sure that the laptop is turned off and the AC adapter is unplugged.

2. Check the connections and cables.
3. Make sure the display is turned on and the brightness is turned up.
4. Ensure that the video cables are connected to both the laptop and external monitor.
5. Restart the computer.
6. Run system diagnostics on the laptop.
7. Try to connect an external monitor.
8. If the computer fails to recognize the external monitor replace or repair the display.
9. If the computer recognizes the external monitor, replace or repair the laptop display.