Yosemite does not recognize external displays...

Similar issues since 10.10.1 update. I have a Macbook Pro Mid 2012 13” non-retina and was running a generic Benq monitor using mini display port to DVI adapter. Had been running perfectly fine. Since the latest update the external monitor display is blank however in displays OS settings it still shows as detecting the Benq monitor. The built-in display appears to try and take on the external display resolution when the mini display port adapter cable is connected. Nothing is displayed on external monitor.

I’ve tried all the resets etc. mentioned in these and in other posts including RAM/NVRAM and SMC resets without any change. I have also tried other DVI adapters though given the multiple posts and similar threads this is obviously an issue caused by the either the 10.10.1 update or possibly Thunderbolt firmware update?.

Strange thing was I was able to get monitor to run on a low resolution using a mini display port to VGA adapter / not the DVI adapter. Though the low resolution is no good for what I want.

I have also tried mini display port to HDMI however I get the same blank screen as when using the DVI adapter.

Would be nice to have a solution for this. I have also tried another generic Samsung display however I get the same results and blank display.

I have the exact same issue with non-Apple Monitors, but interestingly my Apple 27" monitors are working perfectly.

So, my 'home' setup is dual Thunderbolt monitors plugged in to my MacBoook Pro 15" Retina 2013. This continues to work perfectly with Yosemite 10.10.1 installed. When I am out of the office performing presentations for clients, they expect me to plug into their projectors. Since moving to Macs in 2012, a simple Thunderbolt to VGA adaptor has worked perfectly. In recent visits, getting external projectors has been VERY hit and miss, with it working 1 out of 3/4 times if lucky.

I thought it must have been the adapter, so I purchased a HDMI to VGA adapter. Same result.

Then I found this post.

How can resetting PRAMS etc be required where clearly this is something that is happening in 10.10.1. Interestingly, I have worked out that if the monitor is connected to the Thunderbolt /VGA adapter, the monitor is ON before turning on the Mac, and then booting the MAC, and the monitor seems to generally work.

Surely Apple are going to address this.....

Here's what I had to do to resolve my issue:

First, I called Apple Support and did a screen-share with the tech. He could see my second screen and was able to guide me in fishing for the window with the mouse so I could click-drag it to where I could see it. With the MiniDisplayport-to-VGA setup, I had to set the monitor resolution to the lowest setting before it would show up. That was a start, but not a good solution as the low-res made everything large and blurry.

Next, I went to the Apple Store and bought a MiniDisplayport-to-HDMI cable. I then called Support and went through the fishing expedition again, so I could get at the monitor settings window in System Prefs. After that, I changed the monitor input from VGA to HDMI (I'd forgotten there's a button for that on the monitor itself), powered the monitor off and back on, and I'm now running at full 1080p.

Good day! I've been perplexed by this "MacBookPro+Yosemite+2ndDisplay" problem for 2 weeks since upgrading to Yosemite. Today, back at work for the first time, the problem appeared on a different external monitor. Enough! 😠

So, searching through the threads of the Community Forums, I was reminded of the power of zapping the PRAM. Resolved! Well, at least with this second display. Will try it at home tonight.😀

Configuration

Model Name: MacBook Pro, Retina (late 2013)

Model Identifier: MacBookPro11,3

Processor Name: Intel Core i7

Processor Speed: 2.3 GHz

System Version: OS X 10.10.1 (14B25) Yosemite (upgraded in mid-December 2014)

External Video Connector: Mini-display Port to VGA adapter

Monitor: Viewsonic VA2431wm

Wish it would work for me! This is STILL NOT WORKING!! Apple - fix this dang issue!!

Hi everyone,

I'm having this super-annoying Yosemite-can't-see-my-display-even-though-it's-RIGHT-THERE issue as well. I've trawled all the forums (as I'm sure you all have) and none of the solutions worked for me, so I'm going to try installing Mavericks on a partition and see what happens. I'll post an update here.

My computer:

MacBook Pro 2012

OS X Yosemite 10.10.1

Can't detect a BenQ monitor

Mini DisplayPort to HDMI cable.

The same issues with 10.10.1 update. I have a Macbook Pro 15 ⚠

Same Issues here. I connect my Macbook Air to my Dell external monitor. My monitor didn't seem to work after my laptop was in sleep mode.

I tried

- Reboot

- SMC reset

- PRAM reset

- consistently three times the PRAM/SMC reset

- repair disk permissions

- repair disk

- Onyx Automation

Nothing. Even worse. Now the external monitor doesn't work at all. The laptop recognise the monitor in the system preferences, but the external display remain black. When I unplug it from the mini display and plug it back, than it doesn't even recognise it the second time (Like at the old times, after sleep, it didn't recognise). *****!

The console sais this:

com.apple.AmbientDisplayAgent[166]: AMBD Agent: xpc connection became invalid during event handler

I had the same problem. I can confirm that it was the CABLE!!!

After trying hard to fix the issue (SMC reset, PRAM reset, 2 hours on the phone with Apple Support, deleting com.apple.....plist files, repairing disk permissions...) We localised that it is probably the cable. I tried that cable with an other laptop (also under yosemite) and that one wasn't working either. It is a third-party minidisplayport-displayport cable, and however it was working under Mavericks, it has stopped working with yosemite. So the problem is the driver.

I tried than the official mini display VGA adapter connected to my Dell 2210 monitor with a VGA cable and the mini display DVI adapter connected with the DVI cable and the external monitor is working properly with both.

I upgraded to Yosemite and originally I was able to connect to external monitors and tv's with my Thunderbolt/HDMI adapter. However, after upgrading to 10.10.1, it no longer worked. I searched forums and tried I've tried multiple PRAM/NVRAM resets and SMC resets. This did not work. My HDMI to macbook pro adapter is a 10L15S Dynex Mini DisplayPort to HDMI adapter. It seems with the upgrade that Apple is phasing out the adapters (at least in my case). Luckily, I found another thread which lead me to a solution. I removed the adapter, and went from HDMI to HDMI, which wasn't supported previously. This works, and I can finally connect to external monitors again. Here's the thread, hope this helps.

Thunderbolt to HDMI does not detect TV on Yosemite

I'm with Marconi - one shouldn't lose one's peripherals when upgrading to the latest version of Mac OS.

I was puzzled for ages as I have just bought a BENQ monitor and wasn't anticipating any problems connecting it - I've been scratching my head for hours to no avail, searching forums for possible pointers to what I was doing wrong etc. I do not want to spend even more time doing things I've never done before line SMC/PRAM resets etc. That's why I bought a Mac.

Do I give up and take my monitor back to the store and wait until I can afford a very pricey Mac monitor ? It works just beautifully (and instantly) with my son's Windows laptop though so I guess I won;t be allowed to

Holy Smokes!! It's actually working now. I purchased the moshi mini-hdmi adapter from the apple site and Voila. My other adapter (brand unknown) worked fine BEFORE the update to Yosemite and still currently works for my wife's pc. I'm disappointed that I had to spend an extra $35 to make it work, but now we're back to normal. I have a Sharp Aquos 42" display. Im sooooooo glad this issue is freakin over!

So I've still had no luck getting my external display to work despite countless hours wasted searching support forums and trying various PRAM SMC reset combinations etc. Even waited for the latest Yosemite 10.10.2 update which I installed today 28 Jan 2015 (all 560MB of it). Made no difference, same issues with display as previously posted in this thread. Despite having three other Displayport adapters which work with other Windows PC's and had previously worked with my Macbook Pro Mid 2012 (prior to 10.10.1 update) I've decided to order a new adapter from the Apple store. If that fails I'll be trying a format and reinstall of Yosemite, otherwise Mavericks. I will post a followup if I have any luck.

I am having problems too... I had been using my MBP with one monitor at the correct resolution and everything. Yesterday I needed to give a presentation at work so plugged in a projector, now I can't access the correct resolution (either via the native display options or through the Display mode app. have tried several other monitors and cables none seems to work. I did the update yesterday and it still doesn't work. Have also reset PRAM.

HELP!

They have definitely changed something with 10.10.2 Until this morning when I upgraded to 10.10.2 I have run 2 27" Monospace via two Mini DispalyPort to Dual-Link DVI adapter. One of them daisy chained through a WD HD 6TB. Both have worked nicely. The lid has been closed.

Depending on have I start, lid open or not, restart or start, I can get the the displays to work, but eventually they will both go black with no signals. They might have fixed it for some, but I'm now in the crowd that has (two) useless monitors.

I have already had several shut downs with error files sent to Apple, Yak!