Chosen Solution
I have a 2016 Macbook Pro that was water damaged 6 months ago (water bottle spill in a backpack). Unfortunately, it was powered up without inspection and was fried. There is ZERO power getting to the laptop. Any first steps to check? Everything looks perfect in regards to the logic board, etc.
Letting it sit was the worse thing you could have done! So you’ll need to decide how much are you willing to spend on fixing this system. Does it only need a battery? Does it need the logic board repaired or replaced? That may push the costs to the tipping point if it’s badly damaged. What is your skill set? Replacing a battery is not overly hard but I’m sure your logic board has issues from sitting wet for so long. I would at least pull the logic board to inspect it for corrosion damage.
The first thing to go with water damage is usually the keyboard and trackpad assembly, and also the battery, the logic board as long as it wasn’t a lot of water should be fine, at least with older retina and unibody MacBook Pro’s. I would recommend ordering a top case and a battery. Then pray to whatever you believe in. Also do any of the chips on the logic board feel really hot when plugging it in. If so the logic board will need either a couple of chips replaced or the entire board. Also remove the logic board and check for corrosion as Dan said.
