Monitor stops working after 10.10.3 update pleas help

Try resetting the SMC and PRAM

Intel-based Macs: Resetting the System Management Controller (SMC)

About NVRAM and PRAM

This new article has additional notes about 10.10.3 support:

Using 4K displays and Ultra HD TVs with your Mac - Apple Support

.

I just updated my Mac Mini to 10.10.3 this morning, and I'm experiencing the same issue.

I have my Thunderbolt Monitor (connected with a Monoprice HDMI to Thunderbolt adapter) on the left and my HDMI Monitor (connected directly to the Mac Mini) on the right...when I first boot the Mac Mini (Late 2014), the Apple Logo appears on the left monitor, then I get my Login screen on the right monitor (as I always have)...but my left monitor just acts like it's asleep the whole time.

I typically keep my browsers on the left monitor...so I actually had to unplug the Thunderbolt monitor to get everything to kick over to the right monitor so I could see Safari/Chrome and make this post.

I've tried:

1. Unplugging the Thunderbolt Monitor entirely, rebooting, then shutting down & booting again (acts like described above)
2. Plugging the Thunderbolt Monitor in when the computer is already running (just acts like it's asleep)
3. And I've now tried SMC Reset and NVRAM Reset as well...with no luck. (Though I'm not sure the NVRAM reset was successful...I never got the second chime to indicate that it was successful...)

So, I can 100% reproduce what Cthuluh is experiencing as well...I just haven't bothered reverting back to 10.10.2...that seems like more trouble than it's worth...I can live without the second monitor for a while if necessary...I hope that Apple fixes this rather soon...

One theory is that work-arounds you guys needed to get 10.10.2 to work adequately are now interfering with the proper operation of 10.10.3.

I suggest you reset your Displays Preferences under 10.10.3 in one of these two ways:

1) Boot into Safe mode (hold down Shift at Startup) wait while it does a five minute Disk Utility (Repair Disk) while the progress bar moves --typically about 1/3 of the way toward full, then a login screen is presented. You MUST supply your Username and password to proceed. It will now be using temporary 'one-size-fits-all' settings for all your displays, and the Driver is not load, so transitions and re-draws will be slow and jerky.

Actively change your Displays Preferences to something tolerable, and save changes. Close System Preferences. Open Displays Preferences and change the settings to the ones you want to keep, and save changes. Close System Preferences.

At your leisure, restart your Mac.

--OR--

2) Just as above, actively change your Displays Preferences to something tolerable and Save Changes. Close System Preferences. Open Displays Preferences and change the settings to the ones you want to keep, and save changes. Close System Preferences.

At your leisure, restart your Mac.

Thanks Grant. I'll give this a try as soon as I'm done with Monoprice. I'm checking with them to see if there are any known issues.

Now that I've gotten back to System Preferences, I can see that OS X knows the monitor is there, it's just not putting any video out to the monitor.

For what it's worth...I never "configured" anything with I attached the second monitor...it just worked when I plugged it in.

I am confused by this statement" I have my Thunderbolt Monitor (connected with a Monoprice HDMI to Thunderbolt adapter) ".

A Thunderbolt monitor only connects directly to a Thunderbolt port. That port can either be on the computer or on a Thunderbolt pass through on a Thunderbolt device like a a Thunderbolt HD.

DeusPigritae wrote:

I just updated my Mac Mini to 10.10.3 this morning, and I'm experiencing the same issue.

I have my Thunderbolt Monitor (connected with a Monoprice HDMI to Thunderbolt adapter) on the left and my HDMI Monitor (connected directly to the Mac Mini) on the right...when I first boot the Mac Mini (Late 2014), the Apple Logo appears on the left monitor, then I get my Login screen on the right monitor (as I always have)...but my left monitor just acts like it's asleep the whole time.

I typically keep my browsers on the left monitor...so I actually had to unplug the Thunderbolt monitor to get everything to kick over to the right monitor so I could see Safari/Chrome and make this post.

I've tried:

1. Unplugging the Thunderbolt Monitor entirely, rebooting, then shutting down & booting again (acts like described above)
2. Plugging the Thunderbolt Monitor in when the computer is already running (just acts like it's asleep)
3. And I've now tried SMC Reset and NVRAM Reset as well...with no luck. (Though I'm not sure the NVRAM reset was successful...I never got the second chime to indicate that it was successful...)

So, I can 100% reproduce what Cthuluh is experiencing as well...I just haven't bothered reverting back to 10.10.2...that seems like more trouble than it's worth...I can live without the second monitor for a while if necessary...I hope that Apple fixes this rather soon...

Sorry...I should've been more specific.

I have two Asus VH242H monitors that I use. Neither of them has a MiniDisplay Port. One is connected to my MacMini directly via HDMI. The other is connected to a MiniDisplay Port Adapter (made by Monoprice) via HDMI and the Monoprice adapter is plugged into one of the two MiniDisplay/Thunderbolt ports on the Mac Mini.

I was trying to keep it simple by referring to the monitor plugged in through the adapter as "Thunderbolt".

I am having this problem as well and this post is identical to mine. Specifically, System Preferences senses that the monitor is there, it's just not putting any video out to the monitor. I also have grabbed the console output that is generated when the offending monitor-via-DP is plugged in. I can post that upon request. Didn't want to be too noisy here.

I am using a Mac Pro with 3 x NEC E243WMi monitors using the full size DP to a mini DP adapter (compliant w/ DP 1.2).

Worked fine out of the box until 10.10.3.

Monitors: NEC E243WMi

http://www.newegg.com/Product/Product.aspx?Item=N82E16824302028

Cables: 4Xem DisplayPort M M Cable, 15ft

http://www.govconnection.com/shop/4xem-displayport-m-m-cable-15ft/16922456

Adapters: C2G Mini DisplayPort to DisplayPort M F Adapter Converter, 6"

http://www.govconnection.com/shop/c2g-mini-displayport-to-displayport-m-f-adapte r-converter-black-6/17611676

As a workaround, I am using the monitor's DVI output instead with DVI > mini DP adapters.

Apple fixes sporadic startup woes with OS X 10.10.3 supplemental update

.

This update had no effect on my own situation. I would be interested to know if anyone else has successful results with it.