my macbook pro does not detect external display anymore

Same issue here. I just had some success shutting down Automatic Graphics Switching in System Preferences > Energy Saver. I shut that off, and then the Mac discovered the monitor it has happily been working with for months now. It might just be a fluke, but that did the trick this time.

Now, for the day that you could switch to just an external monitor without having to suspend the whole system... that will be a glorious day.

Had the same issue.

What fiesed it was simply leaving the apadter connected to the VGA and while my MacBook Pro was on removing the adapter and putting it back into the mini slot. Worked!

Everything else I tried did not work.

Good luck as this is very frsutrating!

My brand new MacBook Pro with Lion doesn't detect my external Samsung SyncMaster. Following all the suggestions found here and elsewhere, including disconnecting and reconnecting, turning the power supply off and on again etc. does not work. However, if I connect the Mac to my Samsung TV it usually finds it and then I can take the pc back and connect it to my monitor again and it works.

Unfortunately, once the monitor goes into sleep mode for not being used for some minutes, the Mac does not detect it again, and I have to connect to the TV first and then the monitor again.

This is so annoying. I am thinking of buying af new monitor - or maybe installing windows, that had no issues with this external screen.

Regards

You have to unplug the power cable from the syncmaster... then plug in the mini diplay adapter... then do a "detect display" is system preferences to check to see if it's detecting it... then simply close the lid to the laptop and plug in the power to the syncmaster... it will "detect" the monitor and it comes back every time for me now... I've dealt with this issue for over a year.... but it's how I get my external monitor back up every time. Apple and Samsung need to get together and fix this but until then it's the only thing that has worked for me...

Thanks! I'll try that later. For now I've connected an LG monitor. It worked like a charm.

Regards

I had the same problem described by others - my MacBook Pro stopped recognizing an external monitor. At first I dismissed the idea that my mini-display port to HDMI adapter might have suddenly stopped working. However, I replaced it and the problem is solved.

As I said the other day, I set up an LG screen and it worked well. At least, that's what I thought. Today it was almost impossible to get the external screen to show anything, because the MacBook has been in sleep mode running on batteries.

I tried about everything: Rebooting, switching off completely, removing and inserting the Thunderbolt->VGA adapter etc. The only thing that finally worked was the following: Shut down the Mac. Turn it on and close the lid. It will now boot up on the external screen. Now, before it comes to the login page, open the lid again and you should have the extended screen working beside the labtop's screen.

Regards

same here

where?

what do u mean with the synvmaster?

Hey guys i had the same problem with my mbp for months....but finaly got it fixed...

It was defo a software/ firmware problem.....

here is the link with all the downloads i made.

http://support.apple.com/kb/HT4644

after downloading and installing and restarting your mbp, turn it off for 5 minutes, turn back on with no adapters connected.

Then turn on your lcdtv in the right input with the hdmi cable and adapter connected

Now connect it to mbp.

thats how i did and its working after 3 months of trying diferent things....Good luck!

Ps: im using MBP ( early 2011 and 42LG300 )

Hey guys i had the same problem with my mbp for months....but finaly got it fixed...

It was defo a software/ firmware problem.....

here is the link with all the downloads i made.

http://support.apple.com/kb/HT4644

after downloading and installing and restarting your mbp, turn it off for 5 minutes, turn back on with no adapters connected.

Then turn on your lcdtv in the right input with the hdmi cable and adapter connected

Now connect it to mbp.

thats how i did and its working after 3 months of trying diferent things....Good luck!

Ps: im using MBP ( early 2011 and 42LG300 )

Same problems. SanctionOne's solution weirdly worked. You saved me from a trip to the Apple Store, which is an hour away. Gracias!

Well … SanctionOne's solution was working, for about 10 seconds, and then it crapped out on me again. I'm running an Acer V223W.

Same problems as many report. I initially used a Thunderbolt to DVI adapter but the MB Pro was locked up every morning, so I had to do a hard reboot to fix it (otherwise, it was nonresponsive, including unplugging the video adapter). I switched to a Thunderbolt to VGA adapter and that had worked fine for many months, until just yesterday. Unlike with the DVI adapter, I can recover using the VGA adapter. I've tried switching back and forth, unplugging the adapters, rebooting the Mac, detecting displays from the system pref, but nada. Very frustrating.

I have tried the wife's MB Air with the same VGA cord and Display Port adapter, and it drives the Acer monitor just fine.

Grrrr.

kt

So darthkt as you probably saw on my previous post what i did worked for me until today...i tried to connect it again to my LG 42lg3000 as usual but NADA.....

I got upset and i tap, i mean, i PUNCH the adapter ( thunderbolt- hdmi ) and guess what....Working until i disconnected it and try to connect again and now no nothing at all even with punches!

im going to buy a new adapter today and try it. will post again to let you know if was an adapter issue.