Model A1237 or A1304 / 1.6, 1.8, 1.86, or 2.13 GHz Core 2 Duo processor

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Keyboard backlight stopped working after I disassembled my MBA.

I attempted to apply a new thermal paste to the CPU and GPU of the original MacBook Air. After completion, everything works just fine except for the keyboard backlight that refuses to turn on in any situation. The OS X still shows backlight brightness adjustment when I press F5 and F6, but the actual lights won't turn on nevertheless.

These are the components I disassembled

- Battery

- Heat sink

- Port Hatch

- Speaker

- Harddrive

Others were left intact during the process.

Any idea where I might mess up would be greatly appreciated.

Regards.

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Problems covered:

-> ambient light sensor not working at all

-> light sensor only works for keyboard illumination but not for display brightness

-> light sensor only works for display brightness but not for keyboard illumination

-> keyboard illumination works the wrong way round (ie. gets dimmed when room darkens)

Occurences:

-> after migrating an existing user account from another Mac

-> may occur on freshly installed MacBook Air with no account migration

-> after wake from sleep

Solution:

-> create a new user account named "test" with password "test"

-> make sure this user is allowed to administer the computer

-> log out and then log in as user "test"

-> open the Terminal and type this one line command:

sudo cp ~/Library/Preferences/com.apple.BezelServices.plist /Users/YOUR_USER_NAME/Library/Preferences/

-> replace "YOUR_USER_NAME" with the short account name of the problem account

-> enter the admin password ("test") which will not be shown

-> log out and log in again using your own account

-> you may now delete the user account "test" if you want to

The ambient light sensor will now work properly on both the display and keyboard.

How to test if your ambient light sensor is operating properly:

-> make sure you are in a well lit (full daylight) room

-> make sure you enable "Automatically adjust brightness" in the Displays system preferences

-> make sure you enable "Illuminate keyboard in low light conditions" in the Keyboard system preferences

-> set display brightness to max using the F2 key

-> set keyboard brightness to max using the F6 key

-> hold your hand over the tiny holes to the left of the iSight camera

-> the screen will now slowly dim and the keyboard will now slowly light up

Bug remaining:

When putting the MacBook Air to sleep in a well lit room, and then waking in a dark room, the keyboard illumination will work the wrong way round. This should be solved by Apple in a future software update.

You can work around this by always waking and sleeping your MacBook Air in a well lit room.

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Comments:

Thank you for the fast reply. I've looked into the solution but it doesn't solve the problem. But during the process I confirmed that the ambient light sensor is still functioning properly, dimming the screen when I held my hand over it.

My guess is that the root of the problem lies in the reassembling process but I'm not sure where.

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exfictitiouz will be eternally grateful.
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