View Full Version : MBA cant drive monitor with out AC power?

Mar 17, 2011, 12:39 AM
I have a 2010 13" Ultimate. I connect it via HDMI to my 21" Acer monitor and it works fine. Today I noticed that the AC power was disconnected, and it wouldnt connect to my monitor. It was wierd, because if I opened the lid, it would connect and power the external in dual monitor mode, but it would not drive the external monitor as a single screen (I do have resolution set to 1080p. Once I plugged in the Magsafe, it started up the monitor no problem.

Is this a known thing? I didnt think driving a slightly bigger screen would cause an issue like that, I figured it would drain the battery faster.

Its usually not a problem to leave the MBA plugged in when docked to the monitor, but I happened to need the plug for something else this time. Is this how it should be or what?

Mar 17, 2011, 12:57 AM
That's normal. Apple notebooks will not use "clamshell" mode without being plugged in. They will dual screen fine, however. No idea why it's that way.

Mar 17, 2011, 09:37 AM
Here is the Apple support document on clamshell mode:


If you are using a Bluetooth keyboard and mouse on a Bluetooth enabled Apple portable:

Make sure the computer is plugged in to an outlet using the AC power adapter.

Mar 17, 2011, 10:38 AM
Ok cool, Thanks!