2011 iMac 27" EMC2429 Random Reboots

in Genius Bar

I have a 2011 27" iMac (EMC 2429) that continually reboots. It is so frustrating. Computer may work for 5 minutes, or may not even let you log in.

In May, the Apple Store diagnosed the problem as a bad fan.  Two weeks later, the problem started back up.  I deployed for a couple months and didn't want to deal with the issue.  When I got back I decided to try to figure out why it still wasn't working.  

The hard drive was replaced with a fresh OSX install (Sierra).  Problem persists.

Then I took back to Apple Store.  They tested all the hardware. Although the video card was tagged as a recalled card, it passed all tests.  They determined that the logic board needed replaced. After getting iMac home, it immediately did a reboot after attempting to login.

I called the store and they said it could be a bad power cord.  I bought a new one and used it on a separate power location and... Problem persists.

I have tried taking all Ram out and using only one stick at a time to see if that's the issue. Nope.  What could be the problem???


  • Reply 1 of 1
    Given what's been replaced, the behavior sounds like either a sporadic short to ground, or a bad power supply to me.

    If they replaced the motherboard, they ran it at the store for a while. If it didn't reboot there, I'm leaning towards the short to ground. Try bringing it to a friend's house, and see if it does it there both with and without your USB peripherals.
    edited December 2016
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