Chosen Solution
Hello, I have an early 2015 13” MacBook Pro Retina which had water damage. It was disassembled and cleaned out; the battery was replaced with a third-party new one. All seems to work well, with one exception: it will not turn on on battery power alone. It will, however, turn on while plugged in, and then run on the battery once unplugged. Charges fine, too. This is particularly strange behavior. I had previously measured several different points on the motherboard and battery board to ensure everything was working as expected, and that’s all good. Is there a particular point on the board I should look at for this? Is it possible the new battery is faulty in some way? Thanks in advance.
More likely your logic board still has liquid damage. Did you fully remove it? The back side is the side which has the SMC logic which could still have junk on it. I would take the board out and put the board into an ultrasonic to really clean it as the ultrasonic action can get into areas you can’t. If that’s not an option then using a soft tooth brush and distilled water I would carefully scrub the board areas that god wet. Be very careful as you can pull off or damage the small SMT devices. And lastly using flux and a hot air rework station to reflow the components in question. Most of this required gear you likely don’t have so you may need to find someone with the proper tools and the needed skills.
