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Recently I have gotten water on my MacBook Air Early 2014 Luckily the MacBook still works. I turned it off and covered with rice on a tray for a day or so. It turns on and worked for a while. But, then just the other day the internal trackpad and mouse stopped working at the same time. A USB mouse and keyboard work. The thing is, if I’m at the login that appears once you boot up I can use both, once I login I’m unable to use it. I thought it was a software issue at first, but I’ve exhausted all the steps I know including resetting SMC, NVRAM, and upgrading to High Sierra. When I reboot to the recovery mode the mouse and keyboard do not work there. I read online of someone having a similar problem and replaced a cable to get it to work. My question, from my description, what cable do you think it might be? I’d like to get this cable replaced and see if it helps me. Thanks!

Sadly you still had water in your system. Rice really doesn’t work, it only is able to remove moisture from the air making the container is in less humid. It can’t absorb wetness and the longer the wetness sits the more damage it can create. OK so the good news is you still have a chance to fix things here! So far your issue is the trackpad its self. Here’s the IFIXIT guide you’ll need to follow: MacBook Air 13" Early 2014 Trackpad Replacement. Here’s the needed part: MacBook Air 13" (Mid 2013 through Early 2015) Trackpad - Apple P/N 923-0438 As you stated only the trackpad was having problems (keyboard works) I’m sure your cables are OK, Update (10/24/2017) The keyboard is daisy-chained to the trackpad then a second cable carries both signals to the logic board. The probability here is still the trackpad as its the junction of both signal paths. Until you open the system its a guess. I would still focus on cleaning the corrosion and inspect things. Use cotton swabs (Q-Tips) distilled water (not tap!) to clean then hit the spots again with 85% or better Isopropyl alcohol to act as a drier. Do make sure you’ve disconnected the battery first.