I experienced some weird behavior with my 1 year old MacBook today. While I am reading, my MacBook suddenly dimmed to the lowest level (almost went dark). Occasionally, it automatically brightened to the highest level soon after dimming. I was surprised by the sudden behavioral change.
After playing with the power saving setting for a little while and the problem remained, I searched the Apple forum and found suggestions that the automatically adjust brightness feature may be the culprit. This option seems to be on the display option page for some time but it did not cause problem until now. A bug might have been introduced in the latest MacOS update. My Mac is running OS/X Mojave 10.14.6.
After unchecking the box next to “Automatically adjust brightness” on “System Preferences…|Displays” page, the problem did not show up again.
Here is the Displays page with the option.
Besides what I did, others also suggested resetting the Intel System Management Controller (SMC) which does ambient light sensing among other things.
Hope this help!
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