Yosemite does not recognize external displays...

hey dude,

i did what you said in your article:

1. NVRAM reset 2 times
2. shut down and reset
3. rest the SMC
4. restart

LCD is still not recognised. My model is MBP late 2012 13" and LCD is ACER 17" whose standard resolution is 1440*1050.

I found out something during the tests:

• If I select a lower resolution in LCD like 800*600 in mirror mode, LCD is recognized. In other cases, it's not recognized.
• when I plug in the LCD, it's detected by MBP because the screen was refreshed like any external LCD was detected.

I hope everybody here can help me fix it. But new OS causes this low level issue which really makes me disappointed here.

I'm having the same problem. Mini-HDMI output to Sharp Aquos TV worked perfectly BEFORE upgrade to Yosemite. I can't getting it working for the life of me! I've searched all over the net and tried pram/smc reset, repair disk permissions, changed cables, etc. I agree that this is something that apple needs to fix. I would really like this to be fixed!!

Exactly the same issue. My Eizo Coloredge was working fine after installation until (just now) I dared to do a restart...

I have tried various different displays and connections over the past 20 minutes and have restarted my mac (late 2013 MBP 15' Retina) and connected / disconnected multiple times. Neither my Coloredge via Thunderbolt or HDMI (no signal detected) is recognised, nor a Samsung LCD via HDMI.

SO frustrating that something this basic should now be 'broken' when it was fine under Mavericks (and earlier OS). Come on Apple, let's get a fix. Plenty of people rely on external monitors.

Sigh.

I find that it almost always works to turn my external display screen on before I wake up my MacBook Pro Retina (Yosemite). Then the laptop comes on first, and the external monitor a second after.

If I wake up my laptop first, and then turn on the external display screen - that puts the laptop back to sleep. And I have to keep pressing keys on the laptop to wake it back up - can take almost a minute to wake it up again. Sometimes the monitor screen gives me a grey screen with a lot of static noise during this time.

I use an ASUS external screen and hook it to my MackBook Pro Retina (2014) with an HDMI cable. I updated to Yosemite a few weeks ago.

I end up turning my external LED TV off and then back on once logged back into my iMac (after sleep).

Really has started to get very annoying extremely quickly now though.

Any word from Apple on this?

This is not a solution, there is no way I'm even going to contemplate doing this.

The behaviour described in this thread is a bug and the only reason I haven't reported it is because I do not have an Apple developer account.

I'm suffering from the same issue except that I use two different sets of external monitors for work and home. I never have a problem at work using a 27" iMac, and a 23" Samsung as my secondary displays. At home I have two Dell 24" monitors, which are ones giving me problems.

I stumbled on this threadsolving some CPU and memory leak problems, it goes through the procedure of PRAM and SMC reset, except that it suggests doing it in Safe Mode. Perhaps it's worth trying this?

Hi everyone - I spent about two hours on the phone with Apple Support and they were not able to find a solution, even after escalating it to a supervisor. I even showed them this thread via Screen Sharing and they had me try all these steps. I went to Best Buy and just taking a chance bought the J5 Create HDMI/USB 3.0 Display Adapter, model JUA350. I downloaded the latest driver from their site, plugged in, and it worked. I'm connecting the screen via its HDMI port to my USB port. I'm running Yosemite 10.10 on a mid-2012 MacBook Air. The screen is a Dell S2440L. You can also buy the J5 product on Amazon. Hope that helps.

My Yosemite system and external monitor are now working flawlessly. My laptop (MacBookPro purchased last June) now recognizes my external monitor (ASUS, purchased in last July) instantly.

Things started improving about a week ago, and have gotten steadily better, until now there is instant recognition.

Prior to this, every time I turned the monitor on, the laptop would go to sleep and I often had trouble getting the laptop to wake up again, or there would be a lot of static on the screen, or some loud snapping noises over the external speakers. I had to turn on the monitor first, followed by waking up the laptop - but this didn't always work, and there was still a delay before the two would work together.

A few days ago, the laptop fell asleep and wouldn't wake up. Whether it shut itself down, or I accidentally shut it down trying to wake it up, I don't know - but it wouldn't come back on for maybe 1/2 hour. When it did finally turn on, it sent an automatic report to Apple about a restart issue, and another report as well. It was after that, that communication started improving between the laptop and the external monitor. Now, the communication is instantaneous.

I did not have any problems at any time with the laptop recognizing my wireless Apple keyboard or mouse. And the laptop recognizes my iHome speaker (purchased in October) as well.

Sometimes the laptop doesn't recognize my wired speakers that are plugged into the headphone port. These speakers are several years old - I don't know if that is the problem.

Here's another variation:

1. Reboot MacBook Pro with display adapter (HDE brand MiniDisplay-to-VGA) plugged in, but monitor (ASUS VW246) power unplugged.
2. After Mac powers up, plug power in to monitor.
3. Option for mirroring/sharing display now shows up, and monitor correctly identified (VW246).
4. However, monitor itself still says "No input." 😟

~ CP