Macbook Air screen fading randomly between off and full brightness 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?
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