Want MacBook to sleep when lid is closed and external monitor connected

[JackPollack]

I am trying to disable the "clam shell" mode of my MacBook running High Sierra ie. I want the computer to sleep when the lid is closed even when it is connected to power and an external monitor.

After disabling SIP I was able to edit the com.apple.Boot.plist file and add Kernel Flags iog=0x0 as I have done is previous OSs, but the setting doesn't appear to work in HS. Also
sudo nvram boot-args=iog=0x0 from (recovery mode) terminal writes the entry, but also has no effect.

Anyway to achieve lid close - sleep with external monitor and AC power in HS?

 

[ferrarr]

What do you have enabled in System Preferences > Energy Saver?

Another thing to try is NVRAM & SMC resets?

 

[JackPollack]

I have already reset the PRAM and SMC.

Put HD to sleep when possible - CHECKED
Prevent computer form sleeping with display off, Wake for WiFi, Power Nap, All UNCHECKED

But these settings have nothing to do with disabling clam shell mode

 

[Raz0rEdge]

There is no official way of disabling clam shell mode with a setting since it's "automatic" based on what is connected and the state of the lid. To that end, everything you do is essentially a hack of some sort and will work with some versions of the OS and not with others. You can put the Mac to sleep manually, instead of closing the lid, with the appropriate key combo for your machine and OS version.

Short of pulling the LCD cable each time you want the MBP to go to sleep, the key combo is your best bet.

 

[JackPollack]

Short of pulling the LCD cable each time you want the MBP to go to sleep, the key combo is your best bet.[/QUOTE]

No way to get the old NVRAM settings to work?

 

[Raz0rEdge]

It doesn't look like it, since all the indications from my searches confirm your current situation that what used to work in previous versions of the OS doesn't work anymore. Since that was likely a hack or something, it hasn't been maintained in newer versions of the OS. And there is very little you can do to make the OS do what you want unless Apple gives you that control.

The only interesting solution I found was a script that someone wrote to continually use the ioreg command to check for the status of the lid and when closed, they use the pmset command to put the computer to sleep. This also seems to be a bit flaky, but at least it isn't a manual solution and doesn't require you to unplug anything.

The other tweak to the manual situation I found was to unplug the LCD cable momentarily, close the lid which should put the MBP to sleep, then plug the LCD back in and you are ready for next time.