Chosen Solution
The original screen on my daughter’s MacBook Air 2012 (A1369) failed a few weeks ago. I plugged it into an external Apple Display via the display port, and that worked fine. I was able to boot and login. Everything worked normally. Ruling out a problem with the graphics chip, I bought a replacement screen (the entire display assembly, not just the screen) and I fitted that as instructed. And yet it still doesn’t work. When it boots, the screen is blank. I then tested with the external display and that still worked fine. I’ve triple-checked the screen’s connections to the motherboard. What should my next move be? For background, in the past 2 years I’ve successfully replaced the battery and the motherboard. There is very little left of the original device.
Lets double check things here… Take a flashlight and shine it though the lids Apple Logo (a poor mans backlight) are you able to see the faint image of your desktop and its icons? If you do the display its self was not the problem, your real issue is the backlight logic on the logic board and/or the LVDS cable and its connection. If you see the the desktop pop off the bottom cover and follow this guide to disconnect the battery MacBook Air 13" Mid 2012 Display Assembly Replacement Stop after Step 3. Now jump to Step 22 careful disconnecting the LVDS cable look for damage or corrosion as marked here
Are the surfaces clean and undamaged?
