I picked up a 13-inch MacBook Pro late last week whose backlit keyboard wasn’t working. After discussing the failure with the owner and getting the exact details I needed to properly diagnose the machine, I opened up the unit and checked the LCI (liquid contact indicator) for any evidence of liquid or liquid residue. Not finding any liquid, I took the next step in troubleshooting—resetting the PRAM and SMC.
You might notice that your Apple laptop’s screen brightness seems to change in reaction to changing light conditions. I notice this more dramatically on my unibody laptop in a dark room while watching television. The television is a dominant and constantly changing source of light, so the computer’s screen changes brightness all the time. It’s more prominent in unibody computers because the ambient light sensor is located to the left of the iSight camera on top of the screen—its position makes it more prone than the old-style laptops, whose ambient light sensor was under the speaker grills.
Why is this relevant to this week’s repair? Both the screen brightness and keyboard backlight were non-functional. There are three likely culprits in this repair: main logic board, top case (with integrated keyboard), and ambient light sensor. Because both keyboard backlight and screen brightness are controlled by the ambient light sensor, it made more sense to replace that.
Interestingly, the entire display assembly must be replaced if the ambient light sensor goes bad! It’s an officially non-serviceable module, but Small Dog does offer replacement of some parts inside. If the glass covering your display or LCD is cracked, we can fix that for many hundreds less than Apple pricing.