MacBook Pro (mid 2012) can’t start with 3 alarms and sometimes can’t wake from sleep

macbook promemorysleep-wake

I have a MacBook Pro (mid 2012) and I have changed the hard disk to a Crucial_CT250MX200SSD and changed the RAM to CRUCIAL CT8G3S160BM. My Operate System is OS X 10.11.4.

First, I found sometimes my Mac wouldn't wake after sleep and I have to force it to restart. Then after sometime, I found it even couldn't start: black screen with 3 alarms. Sometimes it could start after I tried again, but sometimes it wouldn't.

I have tried to change the RAM back to the original but the problem still appeared. The Genius Bar couldn't found the problem, neither.

This problem usually happened after I put it in my backpack and travel to a different place. So could it be caused by vibration? Actually, when it wouldn't start, pulling the RAM out and reinstalling it could help.

Does anyone have met similar problems? What may be the problem of my Mac? Thank you!!

edit (2017.1.26)

AHT results:

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Best Answer

3 beeps upon startup definitely signals a RAM issue. The problem is that most people assume that only the actual RAM itself can trigger the beeps when in fact there's a chance that it could be the RAM slots causing the issue.

What you're describing to me sounds a lot like a possible solder point issue between the RAM slots and the logic board itself, unfortunately. What leads me to believe this is 1) you've tested multiple sticks of RAM and the issue still occurs, 2) you believe it's happening after transport so things could be shaking loose temporarily, 3) the genius bar couldn't find an issue when running tests meaning maybe when they were testing it the weary solder points just happened to have settled and were making sufficient contact at the time.

Since the genius bar proved to be of no help I would strongly recommend something called an Apple Authorized Service Provider for a second opinion. You can find one using this link (click on the 'Service' block):

https://locate.apple.com/ca/en/

Not to bash Apple Stores but they're busy places. I would try a non-Apple Store location this time as they aren't as busy and aren't trying to shuffle you out in a set period of time to get to their next appointment. They'll likely spend more time with your machine hands-on to get to the bottom of it.

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