Q: My external display is not working since I upgraded to 10.8

In my case my 2011 13" MBP worked perfectly with my Acer display over MDP->DVI under 10.7 but 10.8 it started causing problems. 10.8.1 exhibits the same behavior. It's very erratic, sometimes it works perfectly, sometimes my built-in display flashes for a minute and I have to fall back to VGA. I stronlyg suspect it is related to "best for display" auto-detection.

I am experiencing this problem on a very large scale. I administer about 150 brand new MacBook Pro's and about 700 iMac's of various ages and sorts. All of them have this problem since upgrading to Mountain Lion (via Deploy Studio) and 10.8.1 gave no resolve. They all have connectors (VGA), so it can't be a faulty unit. Last year, on 10.6.8 there was no problem; beamers and displays of all sorts got detected without problem. What i did notice is that cold-booting a MBP with the display or beamer attached it is recognised correctly and workes without problem. To bad it is not always working on the iMac's. I think it has something to do with the automatic detection of resolutions, but I am not sure. I will try adjusting the resolution manually to see if it has any effect.

Similar beamer-, tv-connect problem since upgrading from Lion to Mountain Lion (in my cace just ONE (1!) MBP8,2 , late 2011): Beamers, which I so far connected via VGA do not respond (Epson EB450W Beamers; tried several in school, which so far always responded) and my home-tv via HDMI also does not get any signal. Tried different cables and adapters, disabled gfxCardStatus, used http://support.apple.com/kb/HT5369?viewlocale=de_DE (who knows, why Apple decided to hide the button), tried all options in the dialog-field.

I work with a german 10.8.1, using Airplay with AppleTV3 quite often. The above mentioned system-extension "monitors" seems to me completely changed: Except from different resolutuions all about "AppleTV" und Airplay.

Only when first time - after upgrade - connecting to a beamer, there was a 5 second appearence of the destop on the wall, since then: nothing

Thanks!

Hey guys, this is what worked for me on Mountain Lion.

1. Shutdown your MacBook and make sure to choose not to open any applications or windows that you have open on the restart. I am almost thinking this is where the hang up is.
2. Plug in the VGA adapter only, without the vga cable to the projector, before starting the computer back up
3. Boot up the computer, let everything load on the desktop
4. Then plug in the VGA cable to the adapter.
5. The screen should then flicker and adjust to the appropriate screen res for the projector.

Hope this helps. Please respond if it does.

Thanks,

@neilljobe

This works, but is not a very usefull workaround. My users walk around the building connecting their Mac to all sorts of displays. Rebooting their machine every hour is not the most convenient thing to do.

Manuallt chaning the resolution has no effect. Does anyone have another sugestion?

Since upgrading to 10.8 and then 10.8.1 on my mid 2010 MacBook Pro my Wacom Cintiq 21 display does not show anything, although it works as a tablet only. It's not a fault with the Cintiq as when I plug it in to my wifes Macbook Air running 10.7 it all works fine. Mountain Lion has rendered a very expensive piece of hardware that is crucial to my business completely useless - they must know the problem exists but, yet again, fail to acknowledge it. I am growing a little tired of Apple now having been a loyal customer since the early 1990's. Their customer service is rubbish now. As I write (12th Sept 2012) Apple Mail has been down for over 24 hours and all their iCloud Status Webpage says is that it will be fixed ASAP.

Come on Apple, we are not all 'consumers' of iPads and iPhones, some of us rely on your computers for our business. I need my Wacom Cintiq to work again now, not in six months time. Mountain Lion has been out for a couple of months now and many people have complained that thier secondary displays are now rendered useless or are flaky at best. It's a fundamental requirement for a laptop to have a working external display port - this is a disgrace.

Guys, one other thing I noticed... continue with the following steps and add one in bold writing. This has worked for me everytime I have needed to use a projector with mountain lion so far. I know this is not an answer to the problem or the bug that Apple needs to resolve, but for now this does work. Hope this helps.

1. Shutdown your MacBook and make sure to choose not to open any applications or windows that you have open on the restart. I am almost thinking this is where the hang up is.
2. Plug in the VGA adapter only, without the vga cable to the projector, before starting the computer back up
3. Boot up the computer, let everything load on the desktop
4. Then plug in the VGA cable to the adapter. (Plug the adapter about halfway or 3/4 of the way in, not all the way in)
5. The screen should then flicker and adjust to the appropriate screen res for the projector.

@GISMAC

"4. Then plug in the VGA cable to the adapter. (Plug the adapter about halfway or 3/4 of the way in, not all the way in)"

I never dreamt of reading sorts like this in an Apple-Forum!

Anyhow, as I need to use a beamer tomorrow, I will try it (embarrassing).

Thank You, really.

I agree, but hey I am just trying to help everyone out. I really hope this helps until Apple fixes the issue.

Thanks,

Thanks for the tip!

To update my situation, I can run my NEC P241W as a second monitor ONLY with the VGA-Mini DP adapter or a mini-display port to full display port cable. Using the Mini DP-DVI makes both of the displays look inverted.

However, if I close the lid, all  (VGA, DVI and mini DP - DP cables/adapters work)

I am not experiencing any problems at all with the mini display port to display port cable. I'll assume that will only work for people how have an external monitor with a display port connection.

Apple has not done anything to fix the issue. 10.8.1 did nothing, maybe 10.8.2? It would be great if apple could address this. I give presentations with my MBP, I'll be ok if I run it with the VGA adapter, but if I come across a DVI connection, I'm hooped.

<sarcasm>But hey! new iphone today! </sarcasm>

Same problem here!

Hardware:

Macbook Pro 13" Early 2011

Problem:

After upgrade to Mountain Lion I can't connect ANY external display or projector.

Thins that I've already tryed:

1) PRAM NVRAM reset - DIDN'T WORK

2) Fresh install Mountain Lion - DIDN'T WORK

3) Try others HDMI or VGA adapters - DIDN'T WORK

4) Downgrade (reinstall) Lion - all my adapters and external display worked again

Here is the chronology of the problem:

1) With Lion - Everything worked fine

2) Upgrade to Mountain Lion (10.8.0) - My HDMI adapter stoped work, but my VGA adapter worked fine

3) Update to Mountain Lion (10.8.1) - My VGA adapter died too. Now none of them work. No HDMI and no VGA.

4) Update to Mountain Lion (10.8.2 12C53 - I have an mac developer account) - DESPERATE TRY TO SEE IF APPLE FIXED, BUT NOTHING. SAME PROBLEMS, ANYTHING (HDMI and VGA) WORK.

This issue is back with 10.8.2

I use the HengeDock (a vertical docking station with the lid closed) with my Macbook Late 2008 Aluminium. The issue was resolved 100% with 10.8.1 but the Macbook is back to starting up and shutting down (to and from sleep) when in the external display. The display is NOT broken (and neither is the cable) as it worked fine before upgrading TODAY and I can see the Apple logo during boot.

PLEASE help!

Thank you.

Hi @pkemeling, did you ever find a solution to this? Have you contacted Apple about it? I am in the same boat (but not as many devices!). These major OS bugs are really getting me down now!

gortdromagh

Have you read this thread?:  https://discussions.apple.com/message/17198305#17198305

My own problem with a projector not being seen was to go to system preferences, displays preferences, select the scaled button and then experiment with  resolutions until I found one that the computer/projector liked better than the default.

I haven't had any problem with external monitors other than the projector but  I would like to see the displays resolution preferences come back to the menu bar where it was before mountain lion.

I just wanted to add my problem.

I'm using a Mid2012 MacBook Air running 10.8.2  hooked up to an external Asus X234H through a Minidisplay to VGA connection.

The best output capable of my monitor is 1920X1080 but the MBA can't do anything more than 1680x1050 @ 75Hz.

If I force the external display to 1920x1080, the whole display shifts across to the right. and I have a black border of about 8cm on the left of the display.

I've also tried the restart workarounds suggested here but with no joy.

:-(