Yosemite does not recognize external displays...

I disabled my macbook from going to sleep unplugged everything etc then reconnected it all but my monitor (and my TV which also used to work before the MacOS upgrade) still are not recognised. I have a Moshi min-displayport-HDMI adabptor which I thought was recommended.

I am loathe to go back to an earlier version of the OS. I am living in hope that one day soon I will find a solution so I can use by expensive new LCD backlit monitor

arrgggghhhh - and I can't print greyscale to my colour printer now either - apparently another problem introduced by the Yosemite upgrade.

I wish I'd had warning about these problems and I wouldn't have upgraded my OS

Have Apple said anything at all that anyone knows of ?

Before you hand over your $$$:

1. Ask Apple exactly why they think your thunderbolt port is dead. Ask them to give a detailed technical explanation (even if you won't understand it)

2. Ask them to produce an electronics report of some sort, showing that they have tested the port and that it is not responsive

3. Show them this thread

4. Ask them how they can rule out a software problem when so many of us are having difficulties even when the thunderbolt port seems to be working fine

5. Ask for a second opinion from another Apple person in the store.

Has anyone had any more luck with this issue? I stupidly upgraded my mac book pro (15-inch, Mid 2009) to 10.10.2 and my external monitor connection via mini display port simply died. I have tried everything suggested on here ( the resets, swapping the cables, pressing the option key when display settings are open, disabling sleep mode etc.) and nothing works.

Has anyone had success with the uber expensive Apple adaptor fixing this issue? All incredibly infuriating....

Come on Apple... This problem has been around since Yosemite was first introduced. I didn't switch to a Mac to experience problems I havent seen since windows 95. Took me years to convince my better half to make the switch to a Mac. She was sceptic, but a visit to the Apple Store had her sold. She was promised a great user experience and all this stuff I was sold at your store would just work.."trust us" . Now I have a computer that the monitor won't come back on after it sleeps. Well this isn't "working" any better than the old windows PC I replaced. (At least it would sleep and wake).

I was using mini display port to HDMI to external monitor. It was working for long time but failed after upgrading to Yosemite. It is strange, it did work for some time but failed after couple restarts. I went through trying everything and failed until I changed to using another cable mini-display port to s-video adaptor and s-video to hdmi adaptor.

It works now for few minutes. I will update the post if it fails again.

Replying to my own original post as I hope this will help someone...After hours of reading and trying every reset under the sun apart from reinstalling the o/s, I unplugged the monitor as I read this in someone else's post from a different thread. I waited a little, plugged it back in and now external monitor works again and is recognised.

Sometimes it's the simplest things! 🙂😁

Unfortunately for me nothing so simple. They run all the test and said my 2 ports were dead. So now I'm going to spend 280$ to replace them since my warranty expired 40 days ago. they are going to test also a problem with the hdmi port. It did not work hdmi to VGA but only hdmi to hdmi... Apple mistery

Hey everyone, I'm not a pro but I've found at least one work around/solution.

The problem:

When upgrading to Yosemite the external monitor is not recognized or it flickers or pixelates or distorts aspect ratio (multiple symptoms).

Solution:

I read all the descriptions/posts and fixes and started playing around with un plugging, rebooting, generally everything I could think of that was obvious. I found that turning the external monitor on and off repeatedly will eventually lock it into 1600x1050 resolution and work fine.

I do believe it will be the same problem every time the machine goes to sleep. But at least it is a work around until a permanen hardware or software fix is available.

Hope this helps,

Hooverhoff

Im running into the same problem. Both my MBP 2008, and my MBA 2011 wont pick up my Dell u3014. Tried different cables. Tried both the MiniDP and regular sized, 3 different cables. no luck.

MiniDP to HDMI works ok on both computers.

WTH Apple? Tried NVRAM reset on both machines, no luck either. I want to try the multiple NVRAM resets in a row, but didnt have the time to fiddle with it any more.

Pretty annoyed with this crap.

This worked for me as well. I tried all the resets before this to no avail.

Unplugged the monitor and sure enough... Simple yet sooooooo frustrating.

McCooler and SueSue3,

Due to the panic of not being able to get my MacBook 13 to recognise an external monitor via Thunderbolt to VGA - my brain has become fried and I'm going to ask a potentially silly question.

When you say "unplugged the monitor", do you mean disconnecting the monitor from the mains/power source (wall socket)? Or do you mean just unplugging its adaptor to the Thunderbolt Port?

I'm on the verge of losing the will to live. I desperately needed to use the laptop for a projector based presentation and the black screen of death caused untold panic.

Thanks in advance for your patience and help.

Has anyone else had problems getting the Thunderbolt 1.2 firmware update to work? I keep getting the "please update your Thunderbolt firmware first" warning and I can't get any further. I've followed instructions about having the lid open. Which confuses me. Is there anyone who can use their laptop with their lid closed? Particularly one that you can't connect an external monitor to.

Even at the screen preferences level, it appears as though nothing is connected to the thunderbolt port.

Not happy and grateful for any help.

Many thanks in advance for your help.

Andy

Mac 13 - Late 2011

Yosemite

Thunderbolt to VGA Adaptor

Generic VGA Projector

I did not un plug the monitor, I simply cycle through the on off button a

few times. But I'm using Yosemite. I can't tell if you are too.

Hope this helps.

Hooverhoff

On Fri, Mar 20, 2015 at 4:14 AM, Apple Support Communities Updates <

Hello Hooverhoff,

Thanks for your reply.

I am indeed on Yosemite as well.

On a MacBook 13. 2011 model.

I am away from my laptop at the moment but look forward to trying this on/off/on technique with the monitor.

At this stage, I don't mind if the process is quirky - I just want this to work.

Thanks in advance everyone.

- A

Ok, randomness presents itself again. Now it works with a different cable that DID NOT WORK before.

The one that did work before yosemite, still doesnt.

At least i got it working...so yay? This is both on the 2011 air, and a 2008 mbpro.

I can confirm, power cycling my monitor worked for me.