My Macbook Air (2015 model, High Sierra) screen is dead most of the time but randomly fades in and out. Sometimes it fades rapidly in and out non-stop for a prolonged period, before fading out entirely. The backlight is not dead - it works but is impossible to control.
Please see this video for a demo of the issue.
Does anyone know the cause, or solution?
This is a physical issue.
It could be something as simple as the LVDS connector with corrosion on it that needs cleaning or it's a possible there's cold solder joint or a failing component (possibly both). Only guessing (since I don't have the unit in front of me to test), I would say that it's the 12V power rail that supplies the display that's the source of the problem.
To further diagnose the problem, hook it up to an external monitor. If the problem doesn't manifest on the monitor, the issue has to do with the display and not the GPU.
You will need to take this in for service. If you have Apple Care, this should be covered. If not, you may have some luck with the Apple folks who may service it out of warranty.
Could be hardware, overheating or simply a stuck function key. I would try cleaning it (especially between the screen and the base where the vent is) and making sure keys are not gummed up. Then test the hardware using
https://support.apple.com/en-us/HT201257 pre June 2013 version or
https://support.apple.com/en-us/HT202731 post June 2013
Jonah
