Model A1418 / Late 2012 / 2.7 & 2.9 GHz Core i5 or 3.1 GHz Core i7 Processor

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My logic board is damaged. Now What?

Hello everyone,

First time asking here at IFIXIT.

Last week, my late 2012 iMac's fan started spinning like crazy after power off, which, after some reading, didn't sound too good. I took it to my local Apple support, and a couple days later the news came, and they weren't good at all. The problem was, in fact, a defective logic board. The replacement is 787€ (aprox. 898$). Way too much for a computer with almost 4 years. Because I need it so much for work, I went ahead and bought a new 4K 21,5 version.

Now, the old machine is working just fine, apart from the fact that the fan spins at full speed after power off. According to the tech guys at the Apple store, this is caused by a defective logic board, but I'm not sure exactly when the "problem" will kick in. Again, at this very moment, the computer is running perfectly.

It appears I have two options, sell it really cheap for parts, or just keep it. If I do keep it, is there anything I can use it for, regardless of the defective logic board? Could I, for example, use it as a secondary display? Or will the logic board issue cause the machine to break at some point and I can't even use it for that purpose?

Please bear with me, I'm not that good with all this, and I'm just trying to learn a bit and maybe use the old machie for something.

All input is much welcome!

Thank you so much,


Answered! View the answer I have this problem too

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Had the hard drive been changed? Which fan is acting up?


Hi there. No, the hard drive hasn't been changed. The report I got from the Apple representative says they found a problem in one of the temperature sensors, and that the solution is to replace the logic board. Nothing else.

The machine is working just fine. It's been on since I brought it from the store, and I have done all sorts of work with it since. Is this normal? I thought that a logic board problem should damage the machine completely. But again, I don't know much about this. Is there any test I can do on my end to share with you?

Thank you so much for taking the time.


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2 Answers

Chosen Solution

The easiest way to isolate out whats causing the fan to go wild is to run a program like: TG Pro. Sadly the free version won't offer much anymore, but $16 its still a good deal!

Post a screen shot of what it shows you here so we can see the results too.

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I would suggest first doing what Dan said, then replacing the sensor, these usually only attach to the logic board but are not part of it.

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Rui Guerreiro will be eternally grateful.
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