Chosen Solution
I am working on repairing a MacbookAir4,2. The display will not go to sleep when I close the lid. I can force it to sleep by using the menu. To my knowledge there is not any software issue stopping it from sleeping. I believe it is a hardware issue. I recently replaced the I/O board I purchased from iFixit. This did not correct the issue. What controls the sleep function when the lid closes? Sensor? Magnet? Thank you very much for your help
If you look at the I/O board on the uppercase side there is a component that is raised, this is the Hall sensor which is set off by a magnet in the lid.
If you have the system assembled use a steel paperclip sliding on the displays surface to locate the magnet then carefully fold down the lid to identify the location on the uppercase. Then place a small magnet on the uppercase at this location did the system go into sleep mode? Often I find people switch out the displays with the wrong one so the magnet is not in the correct location. If you continue to slide the magnet along the case surface you should locate the sensors location. If this is the case you’ll need to take the cover glass off to gain access to the magnet and move it. Be very careful as its easy to break the glass! Use a heat gun and picks to slowly lift or just replace the display assembly with the correct one. If you were unable to get the Hall sensor to fire off at all and since you’ve replaced the I/O board already you may want to switch out the I/O cable as I’ve seen a few go bad.
