I use to have this problem. The Thunderbolt would go black and I would have to unplug it from the wall before it would work again... for a short time anyway.
While I can not predictably recreate this, I have stopped it from happening.
I updated my Thunderbolt display settings so:
- automatically adjust brightness is off
- Brightness level is NOT at the max
Note: This is the Thunderbolt display settings, not the MBP display settings. If your display preferences are only showing control for your MBP. Then:
- Close the lid of your MBP
- Open system preferences
- Goto Displays
- Make the adjustments noted above
Prior, I called up Apple support and even brought it into the apple store. They could not stop it. But these changes did make it stop.
Note to Apple tech:
I think it has something to do with Automatic brightness setting. I think when you have it set to maximum brightness and the automatic brightness setting decided to dim the monitor, it dims it all the way down to 0.
This happens in both clamshell and duel monitor mode.
This may not be the root cause, but the setting adjustments I made above have worked for the past month.