Chosen Solution
I have a MacBook 12" 2016 model. It will only power on when AC power is connected. No response from power button when disconnected. The white power LED on the MLB is on with AC disconnected. If I power on with AC connected, then remove the power, the MacBook will remain on. I have attempted SMC and PRAM reset, to no avail. Does anybody have any insight?
at long last, i was unable to isolate any differences between the mb12 logic boards. deferred to apple for warranty repair. thanks for all of your insight!
Go here and enter your serial number from the back to see if it is still covered under warranty: https://checkcoverage.apple.com
Sounds like the power button is not working. Once it is switched on, are you able to turn it off by holding the power button? If not, you will need to replace the keyboard
Since you are set on learning, first step is isolation. Connect a known good battery and test again. Try with a known good keyboard/top case too. Then you can assume it is the board and start trouble shooting the charging circuit. And if you give up at any time and Apple can tell you went inside, they’ll void your warranty. Good luck.
