Chosen Solution
For full disclosure, I got a Macbook Air that was water damaged years ago. Got it 2 weeks ago and it works great with the charger connected to it as it got a bad battery inside that I was able to remove after and will be replacing it. So I disassembled it again, to clean the water stain for just a little and one of the components I just removed was the I/O cable to check and inspect it and snap back into place. I closed it all up again and connected the charger and no light was showing. Then I got this weird behavior, it turned on but no light on the charger and the screen and backlight keyboard open and close in like a cycle of a few seconds then it turned off again. Is there something wrong with the I/O cable that I messed with?
You’ve hit a common issue with this series as the I/O board also holds both the MagSafe connector and the Hall sensor which detects the opening and closing of the display lid by the magnet that is holds and becomes close to the sensor within the I/O board (marked in Yellow] I often need to replace them from liquid damage.
At this point it would be wise just replacing the I/O board MacBook Air 13" (Mid 2013-2017) I/O Board
