MBP not detecting external display

It could be a corrupt preference file. Try the following; in /Library/Preferences find the file com.apple.windowserver.plist and throw it in the trash or drag it to the Desktop. Find also in /Users/yourusername/Library/Preferences/ByHost the file com.apple.windowserver.xxxxxxxx.plist where xxxxxxx is a string of letters and numbers and yourusername is the name on the main user account and throw that in the trash, too (or drag it to the Desktop). Then restart and see if function returns to the monitor.

Hey all, did a software update on my partner's mbp yesterday (10.5.8, security update 2009-006) and had the same thing happen where our external viewsonic display was no longer being detected. Plugging the cable in and out of the mini display port had the same effect already mentioned here where the mbp screen flashed blue like it was about to recognise the external display, but then nothing. Selecting detect displays from display preferences also had no effect. Tried resetting the PRAM and also the PMU, still nothing. So I shut down the mbp; disconnected the mini display cable; then turned off the viewsonic monitor at the power outlet and left it off for 10-20 seconds. Then I turned the viewsonic's power outlet back on, started up the mbp, turned the monitor on and plugged the mini display port cable in and the external display was back and working properly. Have shut down/restarted numerous times since then and it's all still working normally. Not quite sure how/why this busted in the first place, or why turning the viewsonic off at the power outlet seems to have fixed it, but it might be worth a shot for those experiencing similar problems... and it sure beats having to install/reinstall a different os version (which was going to be my next option)!

I restarted my MBP a few times and left the display unplugged for about 15 minutes. Sure enough, it started back up and it's all set. My next step would have been to delete the plist file mentioned here:
http://www.danmyers.name/wp/2009/12/apple-cinema-display-broken-or-wont-turn-on/

It could be that the cable or adapter is going bad and has become intermittent.

NO ONE SHOULD FOLLOW THE POST RECOMMENDING DELETING THOSE PLIST FILES!

if you do, a MBP will no longer boot... you will get a grey screen and might get to the blue screen but you will not get a login screen. I have fixed this issue for others in the past. Specifically, the plist in the by host folder can cause a MBP to not boot if it is deleted.

Here is the test. If you delete the file via finder and you are asked for a password.... STOP! do not delete the file.

If you do delete the file and the mac will not boot properly you will have to put it in target disk mode, replace the file.. or similar, and then chmod and chown the permissions on the file - then your MBP will boot... there are detailed posts out there for this...

Admittedly - deleting plists is generally not too dangerous to a mac... but the com.apple.windowserver plists are different.

I have seen and fixed this first hand... I'll be happy to have it explained to me ...

I've been doing some research, and came upon this topic. I have a Mac Pro 8-core (early 2008) with OS 10.6.2 that I was successfully using with an external LCD monitor via DVI. One day, I booted, and it no longer recognized the monitor, and the display settings no longer had extended desktop options. Tried resetting PRAM, but no go, so I started troubleshooting.

First thing I did was connect my main display to DVI #2 to see if there was a problem with the port, but it booted as if DVI #2 was the main display with no problems, but the second monitor, now on DVI #1, still did not get recognized.

Next thing I did was hook the second monitor to my MacBook Pro (mid 2009 w/ OS 10.6.2) via the minidisplay to DVI cable. The monitor worked fine as an extended desktop.

So, it seems both DVI outputs work fine and the monitor DVI input works fine, but the Mac Pro simply isn't recognizing the monitor. This seems very much like a software issue. Next step will be to use a DVI>VGA adapter (the monitor has both VGA and DVI inputs), I have a feeling it will work. Not sure though if it will somehow reset something so that switching back to DVI will also work.

It's really strange issue, as many people have issues with loss of the second monitor, but it can't be pinned down to a certain situation (as I mentioned, my MacBook Pro w/ OS 10.6.2 works just fine via minidisplay to DVI.

OK...as suspected, VGA works. Same DVI port, same monitor, but using a DVI>VGA adapter and going into the VGA input of the monitor, works like a champ. This HAS to be a bug. By the way, monitor is a Samsung SyncMaster 191T 19" (primary is a 30" Cinema).

Switched back to DVI connection, reboot, and nothing.

So I guess I'll use the VGA connection until Apple works this out.

i have the same problem since i´ve updated to 10.6 on my Quad-Core Intel Xeon 2,8 GHz last night.

immediately after the installer startet 10.6 from the DVD both of my samsung synchmaster 191T (19") turned into black and never come again. they´re connected via DVI to a ATI Radeon HD 2600 XT and worked perfect the last years. but now they´re not detected anymore. if i wire the samsungs via DVI -> VGA-adapter -> VGA-input they work. but not with DVI. i did all this regularly stuff (prram, nvram, smc, safe mode ...) nothing helped.

i tried to wire the samsung with my macbook pro (intel) with 10.6.2 but there happend the same. no signal with DVI. even if recognizes the monitor at least and i can set resolution and refresh rate but no picture on the samsung.

updating my mac pro to 10.6.2 did not help either. thats really bad. i´m not gonna buy new displays cause apple is changing some software stuff and will run the samsungs with VGA until apple releases an update.

i know there could be an issue with cables and as i use very long cables in my music studio to be able to put the mac outside the main room due to noise issues there could be a solution with changing cables. but this is more guessing then solving as i don´t know what kind of cable i should by.

Niddy and Ashler, do the monitors appear in System profiler/Graphics-Displays when connected but not working?

Cheers

Rod

I have the same issue. MacBook Pro \[Original/Intel\] and Cinema HD Display 23-inch.

The Display works on my G5, a Windows Tower/Server and an old G3 17" Mac.
The MacBook Pro works as expected with an external display, in fact two others, but they both use the VGA adapter. The MacBook screen flashed blue when connecting the Cinema display but then nothing works... just left with the laptop's display. Detect Displays does nothing... except make my mouse jump across the screen \[weird\]

I have closed the screen right after the tone... nothing... I have deleted some plist files... nothing... boot with display plugged in... unplugged... etc. All of it works with other VGA adapter displays... none of it works with 23 Apple screen.... very very very very frustrating.

I read elsewhere this problem developed with the 10.5.5 update ... Apparently this didn't occur under 10.5.4. Here we are on 10.5.8 and still an issue... I think older macbook + older screen + older OS = Apple not too interested.

There seems to be no fix out there... I have tried them ALL...

I think I have a similar problem, but then right from the start.
I have a new Iljama 26" monitor and connected it to my MBP. Used the digital cable. DVI-D single link. The monitor has a DVI-D dual link port and my MBP has DVI-I dual link.
When I start up things I get a message on the Iljama monitor: No signal detected
In system preferences- monitors no other monitor is detected.

When I connect thru analog cables and using the MBP adapter cable , I have no problems.

Connecting the monitor to my windows desktop I have no problems with the digital and analog connections. Everything works fine.

So it looks like a Mac issue. Whether it is software or hardware remains to be seen.
But reading the previous posts I think it is software related.
A pitty that Apple does not help in this matter!

peterwillem

Hi,
I have connected my Ilyama 26" to my MBP. With VGA connection no problems, that is working fine.
But the digital connection is not working with the MBP. I have used DVI-D conection cable ,both single and dual link, but neither of them worked with the apple.
Connecting them to my desktop windows pc no problem. The digital conection works perfect.
So I come to the conclusion that it is a Apple MBP problem. But no one from Apple like to confirm that.
It defnitely is not a problem with the monitor. Because my Samsung monitor, now digitally , connected and working to my desktop is also not working (digitally) with the MBP.

It is a shame that Apple does not do a thing about that!
I have a future plan of buying a Mac Pro, but if it turns out that that computer is also not working with other (non Apple)monitors I will definitely not buy that machine.

peterwillem

Same problem here, old macbook pro core duo (2006 i think) and Apple Cinema Display 23" on DVI output (not a mini DVI, regular one).
I didn't use it for a while (before snow L) and last week I took it out, no signal and no detection...
I updated snow L to 10.6.2 and tried alt-apple-PR and it worked flawlessly for a few days, then yesterday no signal...
Screen works fine with PC.
Suddenly (after a lunch break ?) ACD is back, don't know why.
Then next day no detection again, now I can't make it work.
I'd say both are "fine" but can't detect each other easily, sometimes do but don't know why ?
hope sone will find the solution !!

PS I tried to delete the power management plist, doesn't work.
tried several alt-apple-PR, same.
and no
System Preferences > Energy Saver > Graphics > Higher Performance
option available to play with.
I also tried SwithResX but doesn't detect the screen.