Chosen Solution
I got a iPhone 6 from my friend on iOS 8.3! it worked before I trancefered the internals into a new iPhone hushing and new screen, ever since then the iPhone would say it was charging as soon as I plugged it in then abut 3 seconds later it would flash the apple logo then have the black screen with the display on forever, IDK what to do, and I on iOS 8.3 so I wanna save it. Also the iPhone is gold iPhone 6 smaller size, water damaged, 16gb in think.
First thing to do would be to try to replace the battery, as a faulty one would produce the very issues you’ve described. If that doesn’t help it could be really anything, with the little info supplied it would be pure guess to point at anything else.
