Hello, there's much discussion regarding this topic but I'd like to post mine specifically. I have a Macbook Pro Unibody i5 15" (2011 model) and I believe there is liquid damage. It wasn't some negligent beer spill or anything like that. I'm running OSX Lion.
I was wiping down my keyboard like I do every week with one of these sani-cloth germicidal wipes here at the hospital where I work. However, this time I had the computer on in sleep mode (not off) and I think the liquid may have caused damage. When I turned the computer back on, I couldn't type my password in on the login screen, but a few keys worked. Also, the trackpad seemed to be in permanent right-click-pressed-down mode. I did all of the necessary first-aid procedures for this kind of thing. I kept it off, when I got home I removed the back cover and blew the entire inside out with canned air. I then placed the open laptop into a huge bag of rice (I'm asian...so I actually conveniently have a 50 lb bag of rice!). I waited a day, tried to turn it on the next day but the problem persisted. I then took necessary diagnostic steps:
1) I reset SMC and NVRAM, no resolved issue.
2) I plugged in my external keyboard and mouse, and everything works fine on the external components but not on the built in keyboard or trackpad.
3) I made sure mouse-assist was turned off in universal access
4) I went into keyboard settings and opened the "show keyboard strokes" window. Not sure if thats what its called but I'm sure you know what I'm talking about. Where it shows a picture of the keyboard on the screen. Whenever I used my built in keyboard, the screen keyboard changed (number pad on the right disappeared) and EVERY CORRECT KEY lit up when I hit it. They were lighting up and the computer knew I was trying to hit H when I hit H, 4 when I hit 4, etc etc. However, once I tabbed to a typing field, nothing worked on the built-in keyboard. I then tested this window with my external keyboard. The second I hit something with my external keyboard, the on-screen keyboard immediately changed to external and the number pad on the right showed up. So the computer is functioning, it is properly sensing what keyboard I'm trying to use, with the external keyboard and mouse the computer works with 100% functionality, and the show keyboard strokes window even shows the correct buttons that I hit on the built-in keyboard. The built in keyboard just does not type any letters. I find this extremely strange, since I figure It's an external malfunction, and It's weird how the computer senses that I'm hitting the right keys, but the keys dont work when I type them into the field.
3) I rebooted in single-user mode and tested both the built-in keyboard and external keyboard. This is just to see if there is a malfunction with the software. External keyboard functioned 100% properly, but built-in keyboard gave me some keys in place for others, and some keys did not work at all. This is also very weird because when I'm inside mac OSX the keystrokes window on the screen shows the correct letters being highlighted. But even in mac OSX, I can't type with the built-in keyboard.
In conclusion: I've performed all of the diagnostic procedures described in all of the forum posts related to this topic, and I've included the results here so that these aren't suggested ahead of time. What I've concluded (and I'm no expert) Is that because the computer boots and functions 100% with my external keyboard and mouse, that I just need to replace the upper case of my computer. Because if the liquid actually got down to my logic board, the computer wouldn't function at all.
Question for the experts: Am I correct with my computer diagnosis? If so, is there a website you would recommend to obtain a top case or is there a cheaper alternative I might try first? My computer is no longer under applecare warranty so that's out of the question, and I'd like to try to replace it myself. I'm not an electronics major or certified mac technician or anything, but I can follow online tutorials and guides, and I've done work on electronics in the past like replaced my cracked iPhone4 screen myself, which takes at least SOME hands-on and tech proficiency. I'm also a part time worker and full time student and I don't have 500-800 to dish out on a repair.
This is the part I think I need.
If there are any suggestions you have for me, whether its new tests or remedies I can try, or a different part I should buy, or if I'm thinking the wrong thing all together, please don't hesistate to let me know as I will be checking this post often.
Thanks very much for reading!