Cleaning is certainly something to try, but isopropyl alcohol doesn’t restore faulty components and if you have a dim green light after a liquid spill, hardware damage can be given for granted. First part of the power circuitry in MB Airs is on the I/O board, thus it would be recommendable to replace that and the flat connecting cable to start with, also considering fact they come relatively cheap. It’s hard to give advice with liquid damage as when one starts replacing parts without testing on a dead machine it can end in a endless money drain..it’s sufficient a shorted keyboard or trackpad to take down power lines and replacing parts out of guess is an expensive game.