Ignore iFixit guides. They won't help you here, and their prices for logic boards are more than the cost of a used macbook in working condition with the same specs.
The upper left corner of the machine is where the logic board has a connector for the inverter board. Power goes to the inverter board from this portion of the logic board. It is logical(no pun intended) to draw the conclusion that the area of the spill, and the maleffect you are seeing, are directly related.
Using a blow dryer is a terrible, terrible idea. You're just moving junk around the board. Getting rid of it is the idea here. We need something to lift it off, while the board is damp with a material that both cleans, and evaporates.
With any luck, it'll work after you do what's posted below. When the screen comes on for a second then turns right off, it means the inverter board wires are swapped. If you cut the wire going from the inverter board to the LCD, and swap them around, that is what you'll see, which leads me to believe it's an inverter related problem.
If it didn't work after the step listed below, I would try a new inverter with a new LCD. If that worked, I'd swap out the LCD, and the inverter for the old one one at a time to see which worked. If neither fixed the problem, I'd go around the board shorting resistors to each other until the LCD turned on. Once I find out what must short to turn it on, I would use one of those pencils(thanks dimitri!
) that writes in electrically conductive material to create a permanent short, so the LCD always stays on.
If the inverter and LCD panel are both known to be fine, and that issue occurs, where the backlight goes on for a second and then turns off, it is most likely to be fixed by the above method. This is only something I would try on a machine that wasn't a customer's, since if you short the wrong something bad is bound to happen. I would wait until it is unusable to try this.
Then again, not having a backlight does render it semi-unusable. It is up to you. In the meantime while thinking that over, read what I have quoted below. I've posted this many times. I have had a 100% success rate with spill damaged macbooks using this method, but then again no one who has called me has tried to do it themself. Once I hear that someone has tried to fix their own machine, I typically hang up, since that means my life will be twice as miserable.
Try it out. My method is less crude, but this uses household appliances & materials you either already have or can easily obtain/borrow.
Originally Posted by l.a.rossmann View Post
a) Rubbing alcohol already puts you behind the curve. Use 99% or don't bother. Search eBay. I like ultrasonic cleaners like the ones for jewelry, howeverm if you are patient, 99% alcohol works great, with a fresh, hard toothbrush. Do not brush back and forth, brush from the center of a particular location outwards.
b) Stop plugging it in. Each time you do you potentially screw up something else.
c) Do not just clean. It is not the cleaning that is important, but rather, the drying. You can keep the board next to the window or let it dry for weeks and it can still be screwed up. However, half an hour next to a drying tool that does not apply heat to the board will get the job done. It was once I realized this that I had a 100% success rate on the water damage stuff.
If you do not have access to professional tools for part C, a household dehumidifier will work in a pinch. After you're done going through the board with a fine but strong brush & 99% alcohol, hang the board in front of the dehumidifier's intake. Change the side facing the intake once an hour. Do this for about six hours. If you feel the air moving into the dehumidifier from outside the dehumidifier - if you can drop a paper in front of it and watch it get sucked onto the dehumidifier, it will most likely work.
Do the drying right after you have done the brushing, with the board still a bit damp from the alcohol.
Each step is important, the more you deviate from this the lesser the chance it'll work again.
