Strange problem! Intermittent screen "blinks"

[philymel]

Hello

I'm struggling to understand a strange problem. My macbook's screen will intermittently "blink", like a quick fade to black that lasts not even a second. It happens roughly 5-10 times an hour. The screen doesn't go completely black but rather it feels like the display is going to shut off but wakes up right away instead: a little blink! the console messages that always appear exactly when the screen does this are:

kernel[0]: Setting BTCoex mode:7
kernel[0]: Setting BTCoex mode:0

The blink doesn't occur on my external monitor, only on the macbook's screen. I'm using a 15" mid 2010 macbook pro running OSX 10.11.6.

Thanks for your ideas!

 

[Sanpete]

BTCoex is a Bluetooth setting, so not directly related to your screen. If you think there's some connection, you could try disabling Bluetooth and see what happens.

Are you typing or using the trackpad when this happens? That would open the possibility of a loose connection somewhere.

 

[philymel]

Hi, thanks for the reply
I have already reset and turned bluetooth off indeed and still the "blinks" occur. They also happen when i'm not using the trackpad or keyboard and just looking at the screen. So bizarre...

 

[Sanpete]

When you say this doesn't affect the external monitor, are you using both the built-in screen and external monitor at the same time? If not, try turning off automatic graphics switching in Energy Saver settings, which forces the dGPU, and see if that matters.

 

[philymel]

Tried that via gfxCardStatus and it still happens... I now believe it's a sleep/wake issue because when i close the macbook the apple (display) keeps flashing...
[automerge]1589402166[/automerge]
I've already done pram and smc resets... now I'm wondering if it might be the reed sensor?

 

[Sanpete]

You could try something like this in Terminal after the issue has occurred:

log show --style syslog | fgrep "[powerd:sleepWake]"

 

[philymel]

hmm, i get:

-bash: log: command not found

 

[philymel]

ok!
seem to be in the clear from the blinking, at least for now... other things i noticed when the computer was doing the "blinking" was that the battery life indicator was not functioning and the keyboard light would shut off after a while if enabled...
what i ended up doing was following this guide:

SOLVED: MacBook mid2010 A1286 won't go to sleep. - MacBook Pro 15" Unibody Mid 2010

Test after each of the following steps that you haven’t already tried: Step 1  ▹ System Preferences ▹ Energy Saver ▹ Power Adapter ▹ Wake for network access: uncheck. You may need to unlock the preference pane by clicking the lock icon in the lower left corner and entering your administrator...

www.ifixit.com

.

(it's worth noting that i had tried booting up in safe mode yesterday and the blinking was still happening, albeit less frequently perhaps)

before booting up in safe mode this time round (step 6 in the guide), i opened up my mac and tested all the surface connectors to make sure they were all seated properly. while in safe mode after boot up, the computer was able to go to sleep normally and none of the blinking was happening and this continued after opening my login items and various applications. i powered down and powered back up. no blinking as of yet and the computer goes to sleep normally and the battery indicator works!

so, either checking the surface connectors or maybe resetting "powerd" via the activity monitor before booting in safe mode (step 5 in the guide) did the trick (though it was still acting funky after the powerd reset before powering down for the safe reboot)

anyhow, what a strange journey, i still don't know what did it!

thanks Sanpete for your help!
i hope this might help someone else






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