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Hall Effect / Reed Switch Malfunction

Hi Users.

I just got this Model A1398 EMC 2512 that was supposed to be thrown out, it was a god-send because my early 2008 MBP isn’t really cutting it anymore.

Some liquid was spilled over it some time ago and the SSD and Airport card have been pulled from it, but everything else seems to be working fine except that the screen will frequently (1-2 times per minute on average) go black for couple of seconds and then on again. Using the “ioreg -r -k AppleClamshellState” command I’ve confirmed that when the screen goes black, “AppleClamshellState” switches from No to Yes. The machine also works fine with the Lid closed using en external monitor, further indicating the Hall Sensor as the problem. My first idea was a GPU problem, but using gfxCardStatus I’ve excluded that possibility.

So I want to find a practical solution, I would love to not have to buy a new logic board for it so I’m looking into alternative solutions. If I’m not mistaken, this is the location of the Sensor:

Block Image

I’ve tested taking a magnet close to it for confirmation. It looks like it’s soldered to the motherboard. I don’t currently have the tools to take this machine apart so I can’t take a look myself at this time.

So, my question is threefold:

  • Can I replace the Hall Sensor unit with mediocre soldering skills and a soldering iron?
  • And/or, can I turn off input from the sensor into the OS so that it doesn’t cause this issue?
  • Or, is there some other solution to make the machine usable that I’m not thinking off?

I can’t find any “MBP Retina Hall Sensors” on Ebay so I’m guessing getting one and replacing it won’t be easy.

回答がありました! View the answer 同じ問題があります


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I managed to fix the issue (for now) with some help from my brother. There are two visible components on the sensor, a resistor or capacitor and some five legged component labeled “PA3”, I figured that taking one of those off the circuit might disable the sensor while still having it plugged into the socket. So with some help we took the “PA3” out with flux, solder and a soldering iron and made sure there were no shorts on the circuit.

”ioreg -r -k AppleClamshellState” now always indicates that “AppleClamshellState = No”, even with the lid closed. So I can use the machine with the only issue being that I have to manually put it to sleep. Hopefully this solution will not cause any further issues.

Picture below indicates the removed component before removal.

Block Image


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@hregg - So instead of cleaning off the corrosion which is all over the logic board! You messed it up instead!

How about putting the transistor back on and clean your logic board so it works correctly.

Not smart!


Well that's an aggressive answer. That is not corrosion, but dust. There wasn't any liquid spilled in this area of the motherboard. I'd have cleaned it off if I had a proper cleaning agent, but I don't.

I'd appreciate having a constructive conversation instead of being shamed for not having as much knowledge as you might have.



There are a few things you could try:

The first is place a magnet over the sensor so its always engaged. That will require you to use the external monitor all of the time.

Replacing the sensor will require finding the sensor from another MacBook Pro as it’s a custom part.

As far as replacing it does require a bit of skill. Maybe you should find someone with the skills and the part to fix it for you.


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Hi Dan, thanks for the reply.

It already works fine with the lid closed connected to an external monitor so a permanent magnet is not necessary.

I see, so I'd have to get it off a damaged logic board. I'll look into that.

I'd love to be able to just turn it off in software, have MacOS not listen for signals from it. I'd have to research a bit (or a lot) do find some way to do that. I know some people have done it by disabling the SMC, but that's usually just for testing since that turns off a lot of features. I wonder if I can only turn off that sensor and/or adjust the values from the sensor to maybe get it working correctly.




Hreggviður Harðarson さん、ありがとうございました!

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