Q: my macbook pro does not detect external display anymore

Hello,

I bought my mini dvi to hdmi cable yesterday and when i got home i was really happy cause it worked

and today when we really wanted to see a movie on our sony tv it didn't work i almost cried because i really wanted it anyone a bit of help and it seems odd that is breaks in 1 day

It's not broken; bug in the Mac book pro. Mine did the same thing. Working now. I did a number of things. Updated OS, fixed permissions, zapped the PRAM. Then it suddenly worked.

I've been dealing with this same issue for a number of months.  I, as many, went out and bought a new HDMI cord, but the signal from my MacBook Pro still was not detected.  After more random internet searches, I came across a really simple solution/tip, and it worked for me....try switching your HDMI cord around.  Whatever end is plugged into your tv, switch it with the end that's plugged into your computer.  Each end fits perfectly fine into either port (computer and tv), so I had no idea it made a difference, but perhaps it does!

Now I didn't go through all 25 pages of this post, so apologies if this has already been suggested, but again it's what worked for me!

At least I'm not the only one!!!!!!!!

I got home after work yesterday and my MacBook Pro failed to send a message to my Panasonic Viera TV completely after 12 months of no issues at all. I use HDMI to a small connector not sure where I got it from etc.

I know it wasn't the TV because my wife's PC worked fine full signal direct using HDMI.

I spent an hour trying to get it to work with no success; unplugging everything and plugging it back in again. Trying in different order, at the wall etc etc. Today, I even reloaded LibreOffice on my Macbook in case it was some other cause.

Finally I tried again today. I had the TV on, unplugged the little white connector both ends and looked at it, couldn't see anything wrong, reconnected it, and the TV found the signal.

I'm none the wiser. Whether it will work again tomorrow is anyone's guess!

Good luck everybody.

Thanks so much for your post.

I unplugged my new monitor to take my laptop on a trip.

When I returned I could not get my monitor to work - no matter what I did.

Your solution worked!!!

Thanks so much!

Rony

Thank you for your posting!!! This really helped my problem.

Anyone else have this appear sudddenly with no hardware or software changes?  About a month ago I plugged the cable in as usual and no HDMI signal going to my monitor, even though it had worked like the day before... multiple pressing of butttons on monitor kept coming up blank on HDMI input setting.

  sometimes it looks like its catching sync bt then goes to solid blue.  In the past sometimes full desktop would come up on external only. but not anymore...

Am on my third cable configuration so have ruled that out.  Other thoughts?

This is the ONLY solution out of about 20 I've tried to fix this. Don't know how you stumbled upon it but THANK YOU! Was driving me nuts. :-)

Try installing this version of XQuartz:

https://xquartz.macosforge.org/trac/wiki/X112.7.8

Novice at using this apple forum.  Where is the answer? Thanks.

In August 2015 my late-2011 MBP 17" had problems with a randomly-failing video signal to the 27" Thunderbolt display.  (That immediately rules out all the solutions in this thread suggesting new HDMI or DVI cables).  My MBP's extended warranty had run out, but the Apple Store said it was a well-known defect in my model of MBP and earlier, for which there was a recall notice to repair all MBP's, even those out of warranty. This is the "MacBook Pro Repair Extension Program for Video Issues" program,  https://www.apple.com/support/macbookpro-videoissues/ 

I got my MBP back from the store, Apple said they replaced a logic board to fix it.  Back at my office, the external video didn't work on the Thunderbolt display. Not just randomly. Absolutely nothing.  Everything else on the Thunderbolt (webcam, microphone, attached USB devices) worked perfectly when connected to my MBP.  My Thunderbolt showed a picture when connected to a co-worker's MBP.  I tried the co-worker's Thunderbolt on my MBP and that didn't work. I tried all the solutions mentioned in this thread without success. I spent hours on several occasions talking to Apple support. They even talked me into recovering my hard drive from an ancient backup because the video driver was no longer compatible with the new logic board, but there was no other way to remove it from my system.  Even tried switching back to the onboard Intel chipset as recommended by gfxCardStatus.

The external video had gone from failing randomly to not working at all while in their possession.  I returned my MBP to the Apple store, explained how my external display no longer worked since their video repair. I was sick of explaining it over-and-over to someone else.  They reproduced the problem in-store.  Clearly it was my MBP.   They shipped it away for repairs, then Apple called me back after a week and said my 4-year old laptop would cost me $1100 to fix because it was no longer in warranty.  Whatever they did to "repair" it left it broken, or even worse than it was, and now they wanted me to pay for them to fix their FUBAR.

I elevated this to some senior guru (their words not mine) at Apple who said he never gets to talk to the customers.  He was really nice, he agreed with my diagnosis and said he would follow up with their repair guys. The repair guys came back and said my logic board had severe corrosion on it, so it was my fault for spilling liquid on it.  The guru agreed with me that a logic board installed for a week could not be corroded, EVEN IF I DID SPILL LIQUID ON IT.  He said he would "advocate" for a free repair. Then he promptly went on vacation without telling me and all of a sudden my MBP has been returned to the store NOT FIXED. Upon his return he flaked out on me and stopped returning my calls and emails.  That was the last I heard from Apple.

Eight months later, my MBP still works well, except for the video problem. Apple screwed me.   I've had better experiences with used-car dealers.

I hope this is gonna help someone, I tried to use a Thunderbolt/Hdmi with a Hdmi/Vga and after 2 hours, still doesn't work so I tried something else.

I Have a bunch of adapters and I plugged them all together and it worked !

(Picture modified with Skitch)

I had his problem as well, and solved it.  Turned out to be bad cable(s).  As my favorite IT guy says, "check the physical layer first...  I will share with you the best diagnostic tool, worth many times the $10.99 I paid.

There are other versions of this adapter, many with VGA, which I am guessing you don't need.  The one here, and I am a buyer, not a seller (no advertising intention here, you can find many on EBay:

http://www.ebay.com/itm/Thunderbolt-to-DVI-VGA-HDMI-HDTV-Adapter-3in1-for-MS-Mic rosoft-surface-pro-3-2-1-/321715440120?h…

I have an ancient 2006 MBP 15 inch. Today, it would not recognize any VGA outputs to external monitors or projectors but the DVI to DVI connection worked fine. I followed SimcoeAce's advice and reset the PRAM as per his copied directions. After that, my VGA outputs to my external monitors all worked again. I did not do anything other than reset the PRAM with the control-option-p-r key hold down upon startup. I keep nursing this computer along through issues as it ages because it is my baby. This saves me a lot of money and angst at work. THANKS!!!!!

My macbooks are:

(1) MacBook Pro (13-inch, Early 2011)

(2) MacBook Pro (13-inch, Early 2014)

My monitor is Asus PA246.  (2) works and (1) doesn't.  I have done the following:

(1) installed DisplayMenu and switched resolution

(2) reset PRAM

(3) installed gfxcardstatus and switched from dynamic to discrete, and vice versa

(4) toggle cables until my hands were chapped

Nothing works. Any additional suggestions?