MacBook – External Display Won’t stay asleep: stuck in sleep / wake loop

I would pay attention to two factors:

1) Do you have an external keyboard attached?

2) The power situation - how/when sleep happens is affected by this

3) If the lid is closed at the time you move the mac.

A couple of examples will help illustrate this:

Recently I found that my external keyboard was not waking up the closed lid mac as I thought it should. I found that this was because the power was unplugged and the 'lid closed' operation only worked with the power actually plugged in.

As another example I found that when my computer was asleep, in order to wake it up - without opening the lid! - the trick was to plug an external keyboard/mouse in and hit a key / move the mouse. This then took the mac out of sleep (though again that may depend on whether you have power plugged in or not).

You ask for a fix where one of your screens does not wake up. I have a fix for a similar problem as my second screen on my MacMini (server 2011) does not wake up. It's not pritty but it is a fix.

I noticed that the screen wakes up after you change the screens refresh rates, so I use cscreen to do this. After my computer wakes up I run the following script. There are multiple solutions to run scripts just after waking up your machine (like Scenario and Power Manager).

#!/bin/bash
# b.nelissen

# cscreen: http://www.pyehouse.com/cscreen/

# wake up screen when one of these two displays are found
if [ "$(cscreen -l | grep '2b1052d0\|3c0c07c2')" != "" ]; then
    echo "Display found"
    # Dell screen does not wake up, switch back and forth to wake her up
    cscreen -i 2b1052d0 -d 32 -x 1280 -y 1024 -r 60 # small dell screen
    cscreen -i 2b1052d0 -d 32 -x 1280 -y 1024 -r 75 # small dell screen
    cscreen -i 3c0c07c2 -d 32 -x 1920 -y 1200 # big compaq screen
fi

# exit

What it does in short

• Check if the screen is connected (I switch screens between home and work)
• Refresh rate for displayID '2b1052d0' first to 60 than to 75 (to wake up the screen)
• Set the second screen to her normal settings.