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My late-2011 13" MacBook Pro generally doesn't automatically detect external displays. At work or at home, I plug it to either a 23" Cinema Display (2005) or a 24" LG display using a Mini DisplayPort / DVI adapter.

Sometimes auto-detection of the display works out-of-the-box (notably, the first time I plug a display after a reboot), but most of the time I need to manually click "Detect Displays" in system preferences.

My two monitors work perfectly, my MDP/DVI adapter works too (confirmed by cross-testing with other Macs, other displays, other adapters). The problem only comes from my MacBook.

Does anyone experiences the same issue?

  • Model: 13" MacBookPro8,1 (late-2011)
  • MacOS: 10.7.3 (11D50 -- problem occurs since 10.7.0)
  • Graphics card: Intel HD Graphics 3000
  • Software that might affect the issue: iScreen 3.0.0 (even though the problem also occurs with iScreen uninstalled).
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2 Answers

I solved that problem by connecting HDMI cable to another input of my external display. I don't know exactly what's the difference but it works for me.

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Here are some troubleshooting steps you could try to isolate the issue:

  • Run all software updates on both the iMac and MacBook Air. A lot of times there are firmware updates that address issues like this.

  • Reset the PRAM on the MacBook Pro by restarting the computer and holding

    ++P+R on boot but until you hear the POST chime twice. Then you can let go and boot normally.

The PRAM stores configuration information about the displays connected to your Mac, so resetting it may be the answer for you. Try going through these steps and let me know if you're able to resolve the issue.

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All software updates are done on day one, I'm totally up-to-date. As to zapping the PRAM, I've done it several times. On the first reboot after zapping the PRAM, it works; but subsequent plugging/unplugging of an external monitor doesn't auto-detect it. I don't want to have to reset the PRAM each time I plug/unplug a monitor (at least twice a day). –  Cyrille May 2 '12 at 12:09
    
One thing you could try is booting into another OS to isolate whether or not it's a software issue. The easiest way to do this on a Lion machine is to just boot to the recovery partition and connect a monitor there. It should just show you the gray fabric like pattern on the other display, but if it works perfectly there you know that it has to do with either a user based or system based software issue. From there, your steps are to migrate to a new user account or do a reinstallation of Mac OS X. Obviously, if it still happens in the recovery partition, it's time for a trip to the Apple Store –  Matt Love May 3 '12 at 11:19
    
I've narrowed the issue a bit more: when on the login screen, it works. Even when my user account is logged in and the login screen is shown after I wake the computer back from sleep. (I've got an administrator account, but no right to migrate/reinstall by myself as it's a work computer that needs some special setup from my IT department). –  Cyrille May 3 '12 at 11:45
    
Sounds like it may be a user account issue. Do you have access to the guest account (or can you turn it on)? –  Matt Love May 3 '12 at 12:53
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