Chosen Solution
So I bought a second hand MacBook pro mid-2012 on eBay and when I received it it would boot up once after I plugged in the magsafe charger and then I went halfway to the loading screen with the apple logo and then it shuts off. I made sure it was charging and the side battery led’s were on and the magsafe charging light was green and then went amber. so I know its not battery related, I also did a good ole ram card removal and even tried using a different hard drive from a different MacBook i have bought off of eBay but it still wouldn’t work, so I went scouring the internet for an explanation and I believe its the logic board that needs to be replaced or repaired. My question is can I take the logic board out of the other mid-2009 MacBook and put it inside the mid-2012? is it compatible? I found macbooks for parts with logic boards still in them and some that were working i just dont want to buy another logic board because for the price of a logic board i could get a working 2012 MacBook pro lol kinda dosnt’t make any sense on the price side for the logic boards but what can i do lol :)
Make sure the MagSafe LED is green. If you can disconnect the battery, then with nothing connected press the power button a good 15 sec to finish discharging things. Now plug in the MagSafe, your system should spontaneously start up. If it did run the onboard diagnostics pressing the D key. Depending on the OS release it may not work (thanks Apple!) It may end up with a blinking question mark condition otherwise if the drive is missing or no OS is present on it. If it doesn’t startup then it’s a deeper issue within the logic board.
One thing you should check first is the hard drive cable. These have a tendency to go bad, it was more prevalent on the pre-2012 models but I still see the 2012 design fail from time to time. If that doesn’t help, it is likely a bad logic board and I wouldn’t replace that board with anything but a 2012, Apple likes to change little details from year to year and I believe some of the connections are different. The older board also would not be able to run as new of an operating system, the 2009 model maxes out at OS X 10.11.6 El Capitan while the 2012 model will run 10.15 Catalina. On top of all that, the 2009 model still features the old Core 2 Duo processor which would be a significant performance dip from the 2012 options of the Core i5 and i7.
