HT204210: About the OS X Yosemite v10.10.2 Update
Learn about About the OS X Yosemite v10.10.2 Update
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Feb 16, 2015 8:48 AM in response to dmcheechby judysings,Hello dmcheech,
I understand you are using a TV as an external display, and since the upgrade to Yosemite 10.10.2, the TV is not detected, is that right?
The first thing I would suggest is to check to see if there are any updates to your TV that may be needed. Also, restart the MacBook Air and the TV, and try a different HDMI cable to try to isolate the issue.
Check the settings for multiple displays. The article below is for Mountain Lion, but the settings are similar in Yosemite.
OS X: How to use multiple displays with your Mac in Mountain Lion and earlier - Apple Support
http://support.apple.com/en-us/HT202351
Video mirroring
Mirroring displays the same image on each display.
- Make sure your additional display is properly connected and powered on.
- From the Apple () menu, choose System Preferences.
- From the View menu, choose Displays.
- Click the Arrangement tab.
- Enable (check) "Mirror Displays" in the bottom-left corner.
Extended desktop
With extended desktop, your displays are treated as one, continuous desktop.
- Make sure each display is properly connected and powered on.
- From the Apple () menu, choose System Preferences.
- From the View menu, choose Displays.
- Click the Arrangement tab.
- Disable (uncheck) "Mirror Displays".
Closed lid
For instructions on using your Mac notebook with a closed lid and external display attached at the same time, see Mac notebooks: How to use your computer in closed clamshell (display closed) mode with an external display.
Learn more
- To troubleshoot issues with your external display, see Apple computers: Troubleshooting issues with video on internal or external displays.
- For information about Target Display Mode, see Target Display Mode: Frequently Asked Questions (FAQ)
- Quick key commands for video controls:
- Press Command-F1 to toggle between video mirroring and extended desktop
- Press Command-F2 to detect displays
Last Modified:I hope this information helps ....
- Judy
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May 5, 2015 4:13 AM in response to judysingsby rickwoodc,I'm having the same issue which seems to be since updating to Yosemite 10.10.3; my external HDMI display is no longer detected - it no longer appears in the display section of the system preferences, there is no option to mirror or extend the desktop because it's not detected.
Looking at the console, I'm noticing messages saying the display is detected when I turn it on, however the final message is:
com.apple.AmbientDisplayAgent: AMBD: Agent: xpc connection became invalid during event handler
As mentioned the display never appears in the display section of the system preferences. Here's a screenshot of the console:
I've restarted both the external display and my MacBook Air (2011 edition) but with no effect.

