I have exactly the same issue with my 13in MBP after upgrade to Mountain Lion. I have tried to reset the display output to a lower resolution 1024x768, 1024x640 etc but to no avail.
Seriously seriously unimpressed, in Central Asia supposedly delivering a top end training product but now using a flipchart and pen!!!
I got the same problem after upgrading to OS X Lion (previously my MacBook connected beautifully to any projector) and I did not manage to get it going at all. So I was hoping that Mountain Lion would do better, but it appears that I'd better go back to older versions of OS X instead of upgrading.
I thought it was Apple that invented "plug and play". What happened?
I have 10.8 on a MBA 11 and I am able to connect to at least one projector via a VGA adaptor. However, I had to make sure the projector was up and running before I plugged in my VGA adaptor. When I tried to set things up and then turn on the projector, it didn't work.
I am also a bit concerned since I no longer know how to force it to "detect displays". I have to connect my laptop to many different projectors as I travel without a manual override, I am not sure it would ever detect.
I also have a MBA and Mountain Lion. I gave two presentations today and had problems connecting to each of the two different projectors at the venues. In the second case, I had to give up and use a PDF version of my Keynote on a PC!!
My old trustly MacBook (circa 2008) NEVER had this problem. I give probably 100 presentations a year.
Do I need to revert to an earlier operating system?
This morning I resolved my problem. Even though it was with Lion and not Mountain Lion it might be of use to some of you too. Firstly, I learned from the IT guy in my office that my MacBook apparently has an expanded window (in Microsoft's terms) as default value when connected to an external monitor. Then we figured out that it could be corrected, (while being connected to a projector) to look at
System Preferences\Hardware\Display\Arrangement and then make sure "mirror display' is ticked.
That did the job in my case. I know it is not what one expects from Apple, but ............. life is a box of choclates, isn't it.
I had the same problem - tried restarting the Mac WHEN the projector was connected.. ..then the display got detected, and I finished the presentation..
I know that its a workaround, not a solution, but it keeps me going..
Waiting for now for Apple to release an update to fix the issue..
Hope that helps.
Managed to overcome this. Followed AnnEarl suggestion and did as follows:-
a. Power up the projector till it is ready (in my case it was an Epson projector)
b. Plug in the VGA cable to the VGA adapter
c. Plug in the VGA adapter to the laptop
Only then the projector was detected and automatically adjust the display. So far everything went smooth and worked fine for me.
Hope this helps.
Thank you everybody.
73 de 9W2BBS
Have you tried holding down the option key on the display system preference pane as described here http://support.apple.com/kb/HT5369?
I have used it now with several projectors and, while not as easy to use, has worked for me to get the projector connected each time. Just make sure the projector is connected and on prior to trying to detect it.
Exactly same problem. 2012 MBA 11 inch - [Have give > 300 presentations on a Mac) - had to give Grand Rounds this morning. First presentation under 10.8.....NOTHING. LCD projector did not reckognize MBA. Why on earth is "detect display" hidden (press option) - nothing worked - restarting, detect display, changing resolution. PRETTY EMBERASSING - well I blamed Apple. Any suggestions?
OK, now you have me worried. I have done a few presentations on different projectors and have not had an issue (besides having to find the hidden "detect displays"). The next one may be it!
In case it helps, here is my current "procedure".
1) Make sure projector has power and is in standby or powered up (standby preferred).
2) Have Mac running
3) Connect VGA cable from projector to adapter
4) Connect adapter to Mac
At this point about 80% of the time it has sensed the projector and just worked. If not
5) Open system preferences and select diplays
6) On the disply tab hold down the option key to make the "detect displays" button show up.
7) Click the detect displays button
This has worked for me on 10.8 for me so far. Sorry to hear that my lucky days may be numbered!
Prior to 10.8 I had to occasionally have to add the step of setting the resolution to a projector friendly scale prior to detecting displays but I have not had to do that (yet) on 10.8.