Turning off MacBook Pro's display when using an external display?

F1/F2 is better,because open the lid is helpful to heat dissipation .

This issue now reoccurs on 10.10 Yosemite, the previous workaround with the nvram command in terminal doesn't work. Any new solutions for this?

My Friends, when using your Mac on clamshell mode it is really really bad for the temperature of the processor, I had 2 macs burned inside for this issue, one had been repaired by the means of reballing and the other had to buy a new expensive motherboard, when using an external monitor and closing the lid your mac´s temperature rises a lot even when using an external ventilation device, I DO NOT RECOMMEND TO DO THAT my last 2 macs have been badly damaged (processor and motherboard) because of it and I just realized that the problem was using them both in Clamshell mode Do not use it and never put a plastic cover on the bottom part of your mac it really really is a thermal insulation that goes against the aluminum dissipating characteristics, and MAC does not have an opinion on this, they should warn users not to use clamshell mode for long periods of time. for example working.

Thanks

Alex

I agree, this is resolved in my thread here:

Yosemite: Turning off Macbook Pro screen (lid open) with external monitor connected

Turns off the Macbook Pro display while keeping the lid open.

Couldn't agree more. The fan is runnig at max during gaming after connecting TB Display. It took a year for my GPU to burn and getting replaced (Radeon 6750M).

Check out this app: https://github.com/Eun/DisableMonitor/releases

I don't know if it actually does the command line trick, but it definitely works. You only need to disable the backlight by yourself!

Are you sure about this app? In my opinion this app is not working at all. All it does is to place the desktop background of one monitor to the other. The internal display is not switched off by bringing the brightness down. It will still use graphic card resources and age the screen. Or did I miss something?

I just had an idea an would like to hear your opinions:

What would placing a blank black picture (by a fullscreen app, screensaver, whatever) combined with zero brightness do to graphic card and display? Would this imitate the exact behavior of a switched off internal display? Or would the Mac just keep telling the display to keep showing a black picture at 60 Hz frequency?

Any suggestions?

OK, if that is what it does... than it's not what I'm looking for! So isn't there any way to disable the screen without closing the lit?

Hello All,

The MBP senses the position of the screen by a reed switch (magnet sensing) that's located at least in my 2011 MBP 13" just left of the "fn" key and in line with the lower edge of that key. A small magnet placed there will cause the computer to go into sleep/clamshell mode but the display will not be closed.

It could be different on different sizes and years. To find where your magnet is run a piece of ferrous metal (I used the lever on a nail clipper.) down the left and right edge of the display. There are 4? very strong magnets at the top of the display but they're for closure. The sleep sensor's magnet is located about 1/3 of the way down on the display's left edge on mine.

There's always been a controversy about heat flow with the display open or closed. I've had these apart and at least in the Unibodies I don't see much chance for ventilation out the top. (I have pictures if you're interested.) .

Turning the brightness down (f1 and f2) will still leave the display active (Use a flashlight.) so the GPU/CPU is still driving the display even though you can't see it.

I picked a magnet from an old flip case from my iPhone and when I put this on the sensor, the screen goes to sleep. Same effect as when I close the lid, now only the lid is still open and the MacBook can also ventilate on the top. Although there isn't much ventilation on top, it gets quit hot (external display, lot of open programs). I believe the whole unibody acts like a heatsink and when the lid is open it can cool a lot better.

Thanks for this tip!

The way to do it without using a magnet is to enter in the following Terminal command as mentioned in my thread.

https://discussions.apple.com/thread/6601019

I have not tested that, but I believe that the screen is definitely off, isn't it? So when I have no external monitor connected, the screen is also off. Enabling the screen is only possible with an external monitor connected. Or am I wrong?

With the terminal code, yes screen is off if you follow the steps when booting up/restarting and keeping the lid closed and re-opening on the login screen.

(if you don't close the lid while booting up/restarting then the clam shell display will turn on as normal)

If you have no external monitor connected then you wouldn't need to turn off the Macbook Pro clamshell display.

I've always preferred a software solution than putting any 'extra' magnets to achieve this as I don't want to take any chances with things going wonky and loss of HD data.

fridge magnet just left of the caps lock key does the trick. unless thats just way to easy for you.