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Released June 2012 / Core i7 processor with Turbo Boost / Up to 1 GB GDDR5 Video RAM

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After a long period of random crashes, my Mac will not turn on.

Hello everyone,

After a month of issues and troubleshooting regarding my Macbook Pro, I am now turning around the community to fix my problem.

The machine that is causing me trouble is a Macbook Pro 15inch mid-2012 running with Sierra. The only issue that I ever had with this machine was a faulty screen that was changed about two years ago by Apple.

About a month ago, I started experiencing crashes while using demanding Apps like video games, design Apps or watching a movie on my TV via HDMI.

My computer would just shutdown suddenly and after reboot. No error message/crash report would show up. It was like nothing happened and my Mac would just try to reopen all the applications that were opened before it crashed.

The particularity was the pattern of these shutdowns : I would have my Mac running nice for lets say 2 hours, then it would crash. After reboot it would work for 40 minutes then it would crash. After the second reboot it would work for 15 minutes then it would crash again and so on until I reached a point where my Mac would crash just after the boot chime. I would then leave my computer unplugged for the night and I would be able to use it again the following day, my mac following the same pattern again.

I first thought it was RAM/graphic card/logic board related because demanding Apps would cause my mac to shut down no matter what. I tried a few things :

-I first did a clean instal of Sierra to make sure it was not software related. It was really difficult as Mac crashed 3 times in the process. The clean instal seemed to stabilize the crashes for a while then it started again.

-I installed Mac Fans Controller to see if the issue had something to due with the CPU's temperature. My compter would still shut itself down with a cpu temperature of 80 degrees which I don't think is a lot.

-I went to the genius bar but they couldn't run any test because I didn't have any serial number on my logic board.

I was really surprised because I never had any logic board remplacement. They told me that the Apple Official Retailer might have changed my logic board when I had my display changed two years ago.

After some search I have found that my logic board was not changed and that other people had experienced a lose of serial number while updating the OS. So I don't know if this has something to do with my crash issue but I think it is something different. So I used Apple Blank Board Serializer to put my serial number again.

-I managed to pass three extended Apple Hardware Test which said everything was fine even though my Mac crashed during five other ones

-I tried to test my RAM by running memtest86+ which said everything was fine and by switching my RAM on all the different position that I could.

-I changed the Hard Drive and did an other clean instal which ran smoothly and seemed to fix the issue for a day and then my Mac crashed again.

After all of this I realized that the crashes looked more like a power loss. I used a have an IMac and the crashes I experienced with my MBP look like the crash you got from a sudden power loss on your desktop computer if you unplugged it while it is on.

So I started playing with the SMC and realized that a SMC reset would help my MBP to boot again after it had reached its un-bootable phase (crash after the chime).

Something curious as well that happened : My Mac crash and I want to do a SMC reset. I unplug the MagSafe, hold the keys for ten seconds, plug back the MagSafe but then, the Mac will power on by itself, without me having to touch the power button. I even noticed that if it crashes while using the battery, if a do a SMC reset then plug the MagSafe, it will turn on, crash during the chime, turn on again, crash during chime, etc... For 3/4 times before booting completely. (But without me touching the power button)

So I am no expert but all of those strange behaviours seem to indicate a power supply issue.

But then, yesterday, my MBP worked fine for 4 hours then I started a video game to test it. It crashed after 5 minutes but this time, it won't turn on again! Even if I do a SMC reset. If my Mac if unplugged and I try to boot it from the battery, nothing happens when I hit the power button. If I plug the MagSafe, the light turns green and I can hear/see (I removed the lower case to watch) the fans clicking/shivering and I can hear a hissing sound coming from the MagSafe adapter!

I have no clue what to do next and I am afraid I have caused extra damaged with all those turn on/turn off phases.

I would really appreciate feedbacks if you have any clue of what may be the issue.

Thank for reading me, sorry for the long post but I think it is better all the info available. I also apologize for any grammar/vocabulary mistakes as English is not my primary language.


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Just to be honest, im not sure what language you speak but for someone who English isnt the primary language, im quite impressed. This does seem like a weird issue that @mayer or @reecee would know more about


What is the GPU's temp? Also what are your fans doing?

It sounds like your system is going into failsafe mode if SMC reset clears the problem.

While the newer version of Macs Fan Control is better than the older versions it still doesn't give you a clear view on what is happening with your temps as well as TG Pro. I think you'll get a better view on whats happening with TG Pro.


Thank you for the compliment @cam2363

@danj Thank you for answering me. The thing is my Mac won't start anymore so it is going to be difficult to in instal TG Pro. After my first clean instal, the GPU's temp was rarely higher than 80 degrees and the fans seemed to work ok. One day, my mac crashed after 10 minutes of web surfing while I was scrolling down a webpage quickly. So I am not sure it is GPU related


If you can get it back up, there is ways to disable the main gpu and only enable the intel gpu. If you get it back up, let me know and ill give you tutorials on how to do those.


Tell us more about this supposed screen replacement. I say that because I believe it may have been a logic board replacement under a video issue recall program. This may also explain the missing serial number. Also if the machine boots, the logic board serial number will be in the system specs. You may be getting some BS from the Apple people you are dealing with.


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I would deal directly with Apple on this and bypass whomever you are dealing with as i don't think you are getting the real story. Call and ask for a senior advisor. Tell him your story. Apple will have records of just what was done. I think it was covered under this program and still should be:

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I am going to call them and try to know what they exactly did to my machine. Is the serial number written somewhere on the logic board? I know that it is written on the piece that hold the RAM but it is changeable. Is it written somewhere where it can't be altered? I could have a look and check if it is still my original logic board.

Regarding the "MacBook Pro Repair Extension Program for Video Issues", my Mac is a MacBook Pro Unibody Mid-2012 and is not covered/doesn't seem affected by this. It is only for MacBook Pro (Retina, 15-inch, Mid 2012)


The serial number is imbedded into the EFI. If you can get it to boot, go under the Apple to About this Mac. The serial n8umber should be right there. If they did replace the logic board, they should have used software to replace that number (they might not have). Compare the number on the back of the machine with the number your machine reports. Apple will also have full record of the serial number.


Regarding the missing serial number story , I never noticed it before I went to the Genius Bar. I looked at it again and in the system specs it would just say serial number "unknown"

As I wrote before, after the Genius Bar told me I didn't have any serial, I checked again in the "About this Mac" and it was written "unknown" instead of a serial number. But because I thought it was software related and didn't seem to be linked to my main issue, I used Apple Blank Board Serializer to write my serial number back.

Looking back now, I don't think that was the best move as you seem to think this missing serial number is related to my shutdowns issue.


Well. you are not supposed to have that software. You have muddied the waters. Apple repair would have had the number. If I was Apple I would back out too. The people you deal with saw that it had no number and now it does? I wouldn't work with you either.


Yes I understand.

I booked another Genius Bar for Thursday. We'll see how it goes. But now that my Mac is not booting at all they will have to search for the hardware fault.


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Sliver sera éternellement reconnaissant.
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