Answer to: LCD Backlight turns off after booting through grey screenIf this is the same problem I just solved, if you were to plug in an external monitor it would boot to that even though the lid open when you power up the system. Reason: it thinks the lid is closed. This was due to corrosion on the motherboard interface for the small circuitboard that detects the magnet on the left side of the LCD assembly when the lid is closed. The circuitboard also interfaces with the battery connector and is connected to it with a wiring harness. You can leave the screws for the battery connector in place but you must remove the keyboard/touchpad assembly then remove the 4 screws that hold the metal bracket in place that sets against the ports that run up the left side of the motherboard. Then you can back the circuitboard out from the motherboard, scrub corrosion off the connector holes on the motherboard and the interface pins on the small circuitboard, plug it back in and you should be good to go! Happy times.