Keyboard and track pad don't work after login

Hi, I have a customers 2012 Macbook Air come in with the same issue. It's running Yosamite. It does have a liquid ingress event, but all works with the exeption of the keboard/ mouse issue. Upto the login screen the keyboard/ mouse works. Once in the O/S both the keyboard and mouse are inoperative. USB's work fine as plugging in the USB keyboard and mouse work. Steps taken so far:-

1. SMC and PRAM reset.
2. Reinstall of O/S done. ( Yosamite/ El Capitan/ Sierra)
3. Changed the SSD 128GB for another and reinstalled again.
4. Changed both the mousepad and keyboard for known working items
5. Placed the motherboard into the full casing of another Macbook Air.
6. Placed the working motherboard into the original casing.

Results were 1-4 = same outcome, once at login screen they both work but not after. Placing original motherboard in the donor casing, same result, donor motherboard into original casing----- works fine. So, I am at the point of condeming the motherboard.

I have also run a clean install from another hard drive by removing the SSD and pressing the ALT on power on then choosing the hard drive, again with the same results.

The unit has been passed to an Apple store and they have said the motherboard is the issue.

Thing is I am like a dog with a bone..... I need to understand how the keyboard and mouse work fine ( all keys operational at the login screen as is the mouse) yet as soon as you his the desktop they fail.

Is there something I am missing??

Hello jhspies,

After reviewing your post, it sounds like after you updated there are a few things having trouble. I would recommend that you read these articles, they may be helpful in troubleshooting your issue.

Intel-based Macs: Resetting the System Management Controller (SMC) - Apple Support

OS X Yosemite: If keys on your keyboard don’t work

Intel-based Mac notebooks: Troubleshooting unresponsive trackpad issues - Apple Support

USB and FireWire Quick Assist - Apple Support

Thanks for using Apple Support Communities.

Have a nice day,

Mario

Hello everyone,

This is my first post to this forum, so I apologize if I have done so incorrectly. But I am writing in order to document my successful resolution of this problem! With great gratitude! I read and tried many different solutions, over the course of several months, and was finally told by Apple support that it was a hardware problem and that I likely needed to have my trackpad and keyboard replaced. But it never really made sense to me that my keyboard and trackpad could work for the login screen (but not after), and for it still to be a hardware problem. Not really wanting to pay $400 or so, I had finally resigned myself to using an external keyboard and wireless mouse.

Let me end the suspense and just say what finally worked: uninstalling Firestorm and my Second Life Viewer! I just did it on an intuition, remembering how often they made the computer freeze up. Now everything works fine again.

I hope that Apple (and perhaps Firestorm) will investigate how this particular bug could remain, despite my endless restores from Time Machine, trying every operating system from El Capitan back to Mavericks, wiping the hard disk clean and starting over [!], trying every sort of recovery mode, hardware diagnostic tests, clearing the PRAM, etc, etc, etc. Believe me, I tried every remotely connected suggestion, from every forum I could find.

I have a MacBook Air (13-inch, Mid-2013) currently running OS X El Capitan 10.11.1. And I feel like I just got my computer back.

Sad to say, my problem has returned! I had my computer back for two days, during which time it worked flawlessly. I'm thinking it has to do with it going into sleep mode (some people report keyboard problems related to sleep mode), or maybe some app was updated which is causing interference. If it is the later, I can't find it.

I would say my uninstalling firestorm and the SL viewer was just a coincidence, but the keyboard starting working again IMMEDIATELY afterwards.

You can tell I'm grasping at straws! Any suggestions would be appreciated!

I did had same issue. I have remove "Swipe" app and keyord is working fine again.