El Capitan Won't Detect External Display

[jumapili]

I have 2 samsung monitors that worked fine before I installed the beta. Now I can't get the external display's to detect.

Have tried to pram and smc several times.

 

[revokin]

I have 2 external displays on my 5k iMac. I can only get the iMac display and 1 external working. Can't get all 3 going at same time.

 

[jumapili]

Are they the same type of monitor? Did the one work automatically? Or what did you do to get it working.

 

[revokin]

Both externals are the same type of display (Hanns-G HG281D). I didn't do anything to make them work, they just come up when I plug them in. Only issue is it only detects 1 of them, whichever I plug in first.

 

[jumapili]

Interesting did you try the smc and pram? Did you click detect display in Display preferences? You know you have to hit opt for that button to come up right? I also have a 5k iMac. I have tried all of this to no avail.

 

[revokin]

Tried all of the above. Can only have 1 external display at a time. If I have all plugged in and unplug the current working display the other one pops right up.

 

[jumapili]

Well you are doing better than I cause I can't get either to work

 

[keviig]

Same here. Can't get my external monitor to show up, even after trying all of the above.

 

[jumapili]

So I am going to go purchase a new monitor just to see if it will work. If not back to the old os

 

[campyguy]

revokin, members in Apple's Dev Forums are reporting non-functional displays connecting via HDMI.

I have two Dell P2715Q displays connected to my rMBP via mDP-to-DP cables - both work as expected and without issue at up to 4k @60Hz in either portrait or landscape mode or a combination of both with my internal display working perfectly, with no additional drivers or software installed. No lag.

 

[S.B.G]

FWIW, I'm using a Dell P2213 connected to my 2012 cMBP and its working fine for me. I'm using the mDP to DVI adapter to connect it.

 

[jggann]

FWIW, I'm using a Dell P2213 connected to my 2012 cMBP and its working fine for me. I'm using the mDP to DVI adapter to connect it.

I have two Dell monitors on a late 2013 MacPro. One is a 4k Dell P2715q and other is an older Dell U2711. After installing El Capitan, the 4k monitor will not work at all. The older U2711 works fine. I have tried the 4k as a single monitor, switched cables, initiated detect display, etc etc.....no luck.

 

[jggann]

Adding to my above post, I am reinstalling Yosemite on the Mac Pro now and assume my P2715q will again work fine upon reversion to Yosemite. Meanwhile, also have El Cap installed on 2013 MacBook Pro. Noticing some wifi issues....lose connection, but then comes back. Whole system seems more sluggish than Yosemite....may revert MacBook back to Yosemite as well.

 

[jggann]

OK, my third post and I have a suggestion for people whose monitors aren't being detected. After much effort at trying everything from resetting PRAM (or whatever its called now) , Smc, changing cables, etc. I finally got both of my monitors working on El Capitan by merely unplugging the power cord to the monitor that was not working and plugging it back in a after a few seconds....not sure, but monitors must have something similar to resetting smc on MAC. Anyway, both of my monitors are working fine now and the 4k monitor shows the Apple startup which it did not do under Yosemite (this is a well known problem with Dell 4k monitor under Yosemite).

 

[jumapili]

Okay So I went and got a Dell S2715H so it is HDMI instead of DVI on my 5K retina and when I left one of my Samsung 245bw's plugged in when I rebooted the both external monitors came up. So I shut down and put the Second samsung back on and booted nothing. Okay for me this problem is solved unless when I go out and get a second Dell S2715H two of them don't work.

Btw this Dell 2514h looks great.

Also... jggann that is called smc when you unplug...

https://gigaom.com/2011/07/26/when-to-reset-your-macs-pram-and-smc/

 

[revokin]

I just hooked up both my monitors to my 2012 rMBP and they both came up fine. It's something with the 5k that doesn't play well with both of them. I've tried mDP->HDMI and mDP->DVI.

 

[revokin]

Anyone with issues try PB2 and have it fix it? I ended up going back to Yosemite but would go back to beta if display issues were resolved. Everything else worked great for me.

 

[Baastian]

Anyone with issues try PB2 and have it fix it? I ended up going back to Yosemite but would go back to beta if display issues were resolved. Everything else worked great for me.

Installed El Capitan this morning.
And promptly my external display does not work.

Also forcing to re-detect (hold the 'option' button pressed in the 'Displays' preferences screen), does not detect the screen anymore.

I tried HDMI port, Thunderbolt -> DVI, makes no difference.

Anybody else successfully got their external display working?

 

[hurley999jb]

Installed El Capitan this morning.
And promptly my external display does not work.

Also forcing to re-detect (hold the 'option' button pressed in the 'Displays' preferences screen), does not detect the screen anymore.

I tried HDMI port, Thunderbolt -> DVI, makes no difference.

Anybody else successfully got their external display working?

I am connecting a mid 2013 Macbook Air to a ~2010 27" iMac via mini display port - I got it to work by unplugging the monitor and replugging it in, for whatever reason seems to reset it like others on this thread suggest.

 

[Tomasseee]

I am connecting a mid 2013 Macbook Air to a ~2010 27" iMac via mini display port - I got it to work by unplugging the monitor and replugging it in, for whatever reason seems to reset it like others on this thread suggest.

It does not work for me, i unplugged, replugged, torned of and unplugged replugged the monitor, SMC,PRAM reset and so one, but does not work It works flawless under Yosemite

 

[h9826790]

I am on the other extreme, even my 4K TV is switched off, 10.11 still detect the TV and sometimes make my mouse disappear (the pointer move to the screen that is off).

It is a bit annoying. Also, with that 4K TV detected, there will be a little bit lag in system UI when exit from mission control (enter mission control is normal).

 

[riceforlife]

It does not work for me, i unplugged, replugged, torned of and unplugged replugged the monitor, SMC,PRAM reset and so one, but does not work It works flawless under Yosemite

I'm having the same problem with a Dell monitor connected to an iMac 5K via mDP to DP. Would love to hear if anyone figures out!

 

[bug]

Same problem for me - just upgraded and my Dell monitor is no longer detected.

 

[llirik]

I am now having this issue as well on el capitan after upgrading from yosemite, on 2015 retina iMac. I even specifically waited for a .1 release of 10.11 to hopefully not have launch issues.
On yosemite, it was working, but i had to turn off/on the monitor after ever restart/sleep, but it would work.
now, nothing I've tried works.

- thunderbolt to dvi = no joy
- thunderbolt to hdmi = no joy
- thunderbolt 2 dock, direct hdmi to hdmi = no joy
- thunderbolt 2 dock, thunderbolt to hdmi = no joy
- thunderbolt 2 dock, hdmi to dvi = no joy

tried pram, smc reset. tried my old trick as well, no luck.

interestingly, thunderbolt to hdmi on my 2015 retina mbp works. so does hdmi direct. same config on iMac as above does not.

it's a dell monitor (2408wfp).

 

[quixani]

Wondering if anyone can help me. I have an early 2008 imac that I just updated to el capitan. I would revert back to the previous os except my time machine doesn't seem to be working (separate issue). So my problem is that I used to hook up to my very old tv but now it's not detected under display. I hold command and hit detect display. I have tried unplugging and re-plugging in the cable (hdmi?) but am unable to get my computer to mirror to my tv.