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

Since upgrading to Mountain Lion, I am unable to plug my Cintiq 24HD monitor into my mid 2011 MBP 13in and have it wake properly from sleep. It turns on then off immediately.

Hi there,

I had posted this as a question on my own, but no one has followed up to it. Anyway, this is the issue that I'm experiencing with my external display

Everything was working fine the day after updating to 10.8 when I hooked up my NEC monitor to my MBP (mid 2010) with a DVI-mini display port adapter. However, when I hooked it up to the closed MBP the next day, it refused to wake when tapping the bluetooth keyboard or trackpad. When I opened the MBP, the screens came on, but looked inverted. What was red, was blue... the blue folders where golden, etc. But it wasn't a true inverted, like when you check the box in the accessibility panel. Because I looked there, nothing was checked. When I clicked the box, it went to a "true" inverted appearance.

I unhooked the monitor, the MBP screen appeared normal. Plugged the NEC back in and it appeared inverted again. When I mirrored the monitor, however, everything was fine.

A quick fix thus far has been the VGA adapter, everything is fine there. I can have both the MBP and the NEC running as per normal.

A call into Apple under my apple care proved to be fruitless... the suggestion was to zap the pram and smc, both not rectifying the situation.

The apple tech walked me through a remote restore restart. There, the monitor hooked up to the DVI-mini display port was working absolutely fine! I opened the lid while in the restore partition, and bingo! it was working fine. SO hardware can not be the problem, nor can the adapter be faulty.

But I was still  told it might be a hardware issue and to bring it in under apple care. I was told if they can't replicate the situation in-store, that they'd be able to escalate the issue to the engineers.

Before I updated, I cloned my system with superduper!, a bootable backup of 10.7.4. I figured I'd check to see if the issue was present in Lion. It isn't. I believe this to be a bug in Mountain Lion. However, the solution from Apple is to still bring in the MBP to have a genius take a look around. Frankly, my three phone calls over the issue to apple should be enough to make some notes and send the issue off.

I'm usually a dual screen worker, so I'm not at a loss. But this seems to be a bug that isn't being acknowledged.

I was about to attach a screen capture to show what I'm talking about, but uh, the screen capture came up normal on the main (external display) and inverted on the secondary (MBP) display. So, it must be software related. perhaps a third party program and 10.8 not playing nice together. But why only affect the DVI connection?

Anyway, I decided to see if the issue was present when I changed which monitor is the main display. It's still wonky. I changed the rotation to 90 degrees and everything is back to Normal! Aside from the fact that I'm looking a 24" screen in the vertical position.

I really don't want to do a fresh install... but I may have to.

That's what is going on with me… so yea, not case closed.

I'm having a similar problem. I hook up my 2011 13" MBP to an HP LP2475w. I used to use a display port connector, but since upgrading to 10.8 after about 3 mins the display loses the signal, and refuses to reconnect, no matter how many times I disconnect/reconnect. This didn't happen under Lion.

Using a DVI adapter things are a bit better, but I randomly get half a screen full of random noise, about once or twice a minute. Hard to say if this happened under Lion as I used to use the display port connector...

Same problem here with an Acer display, hangs on boot (with the external display showing gray with a mouse pointer that moves). If I boot without the external display, boots fine but plugging in the external display the MBP 2011 cycles like its trying to expand the desktop repeatedly.

FYI using a VGA adapter works fine for me, I am guessing it is having trouble introspecting the display's capabilities.

Yes. Same thing as you, Chris Knight1.

Anyone else have my issue? MBP won't wake from sleep after connecting an external display while it is closed?

Reinstalling Mountain Lion once again resolved the issue for me. Apparently, this external monitor compatibility issue is not unique to mountain lion but a number of people had in fact indicated that they were having this exact problem when they upgraded to Lion as well.

So random...

Friday I couldn't get the external display to work at all with the DVI cable. VGA worked fine. This morning, booted and plugged in the DVI cable and everything is happy.

I have a strong suspicion it's related to the "Best for display" resolution auto-detection that was added in Mountain Lion as it is able to recognize and use the display but the OS gets into confused states.

For what it's worth, just reinstalled 10.8 from scratch and... it still does exactly the same thing. DisplayPort loses the signal after 3 mins, DVI shows random crap (tried two different DVI connectors and 2 different cables). VGA adaptor arriving in the post tomorrow, we'll see if that's any better...

I have exactly this problem - at home I have a 23 inch cinema display + displayport adapter - at work at 24 inch cinema display (natively with display port). BOTH exhibit the same behaviour since 10.8, ie when you open the lid the laptop screen activates regardless of whether you want it to.

The old behaviour was much better - it provided a way of shifting everything onto the big screen and keeping the MBP screen turned off should you want it to be.

Same problems here.  I am on a 2012 MB Air with a mini display port to DVI adapter cable feeding a Mitsubishi projector.  Sometimes it works, mostly it doesn't and there is no set patterns as to why.    On my old 2008 MBP running 10.8 and a DVI to DVI cable it drives the projector much more reliably than the MB Air with the mini display port.

I definitely do not like the new displays preferences and think the programming for same must have a bug.  Also, Why did Apple  remove displays preferences access from the menu bar?  It was working fine in 10.7 and was much easier to select resolutions.  Hope they fix this real soon or else I will have to go back to OS 10.7. 

Correction to my previous post.  My 2008 MBP that works properly with the projector is still on 10.7, not 10.8  Mountain Lion.

I'm happy to say that the VGA connector worked! Not as crisp as displayport or HDMI, but no cutouts or garbage, and totally solid.

10.8.1 Seemed to fix my issue. I can plug in my Cintiq 24HD display while my MBP13 is closed, and successfully wake it from sleep.