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2.0GHz, 2.3GHz, or 2.6GHz quad-core Intel Core i7 processor (Turbo Boost up to 3.8GHz) with 6MB shared L3 cache.

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Replace reed switch/hall effect on MacBook Pro


I have a Macbook Pro Retina (a1398), and I need some help.

A few days ago I closed the Macbook lid, it went to sleep, but the I opened it back, it never came back on.

I tried to force a restart but the power button did nothing. It seemed like the mac was dead.

I opened the bottom case, disconnected the battery, and connected the power cable and the mac started ... I can ear the mac chime, but the screen turns off after a second and it never shows any image.

I did a PRAM and SMC reset and the problem still persists.

I connected a external monitor and I can see everything on the external screen.

I tough it was a LCD issue, but then i noticed that the keyboard and trackpad stop working a few seconds after the OS boots. If I connect a external keyboard and mouse I can work normally.

So I believe that my Mac thinks it has the lid shut. That's why it shuts down the screen after a second or two when it boots, and when the OS boots, it shuts down the onboard keyboard and trackpad.

I don't know if this mac uses a reed switch or hall effect sensor. I searched Google but I wasn't able to find anything about this macbook model, so i could replace the defective part.

Can someone please help?

Thanks in advance.

Update (03/19/2018)

Hi Dan thanks for your reply,

The bottom cover has been off since I started having these issues.

Here is the result of CoconutBattery (yes, I let the battery fully discharge on as a test).

Block Image

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I found another thing that supports my thoughs on the problem being with the reed switch/hall effect.

When I am connected to a external screen OSX is running in clamshell mode.

Clamshell mode is activated when you close the lid and it requires ac plugged in... if you remove the ac, then the laptop will go to sleep.

This is happening with my macbook. If I remove ac, it always goes to sleep... if I plug it back in, it will resume (only on the external screen)

I installed InsomniaX and activated Disable Lid Sleep option which changes the OS so that it doesn't go to sleep if the lid is close.

After that removed the ac plug and the laptop stayed on.

So the macbook is detecting that lid is closed. That's why if I remove the AC (without InsomniaX running) it goes do Lid sleep.

Is there any way to test the hall effect sensor?


Another thing

If I run on terminal the command ioreg -r -k AppleClamshellState I get:

"AppleClamshellState" = Yes

This states that Im in clamshell mode when that should not happen when my lid is open


I have a very similar issue. MacBook Pro Retina 13-inch Late 2013. Everything works on it great. It powers on, it boots up, and everything works. If i put the computer to sleep manually via the Apple menu - no issues, it wakes up with the stroke of a key. If I close the lid or simulate closing the lid with a magnet, it will go to sleep and WILL NOT WAKE UP. I can't even hold down the power button to shut it off and restart it. I have to open the bottom, disconnect the battery, do an SMC reset (mandatory), plug it in without the battery connected, and then it will power on. I will have to immediately do a PRAM reset or it will boot to the recovery partition. Any help would be greatly appreciated.



In my case it was the motherboard, and unfortunately I had to replace it (not cheap).


That's what I'm doing...


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While it may not seem it you likely have a battery failure. What happens is the battery swells up pressing on the keyboard & trackpad.

Run this: CoconutBattery and paste a screenshot here for us to see.

As far as the display I'm suspecting the backlight logic has an issue but before we deal with than lets pop the bottom cover and see if releasing the stress helps things.

Update (03/20/2018)

mmm... Well the battery does look good and the fact the terminal command states the sensor is in the closed lid state when it should be open does point to the Hall effect sensor being bad.

Sorry to say I've not needed to replace the Hall effect sensor in the retina systems yet. Apple does tend to hide them well ;-{

In reviewing the schematics for the early 2013 model (I don't have the late 2013 model) here is what I found

Block Image

I'm not sure where the sensor is located its either on the uppercase or its in the lid. In reviewing the possible locations I can only surmise that one of the speakers has it or the display lid. I would recommend you try to locate the enabling magnet using a paper clip running it along the lids display sides. Then carefully fold the lid down a bit so you can translate the location to the uppercase. I can tell you the front edge has the magnet & plates to hold the lid shut.

Update (06/12/2018)

Here’s the location of the Hall sensor on the main logic board:

Block Image

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Hi Dan,

Yes I've seen that schematic, and also seen the board view, which looks looks like it's a chip in the logic board :(

I trying to figure out a was to disable the sensor, with partial luck so far. I'm able to disable all SMC sensors, that results on the laptop screen working normally because the lid sensor is disabled, but all the other sensors like temperature are not working, which is not ok.

Thanks for your help.

If i figure something out I'll update this thread.


Thats the sensor in the schematic, there's no board view for it just the connection point to the logic board.

As I said the sensor is hidden either within the speaker or in the lid with the iSight camera.

Disabling SMC is a bit much... I would focus on locating the sensor using the paperclip and a magnet.


"Disabling SMC is a bit much"

I know, I did it as a test to make sure the screen was indeed working.


That's OK, didn't want you to throw the baby out with the wash water ;-}


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Same issue here (rMBP 13 Early 2013), even worst with the display, together with the keyboard light, blinking from on to black. As in your case, the keyboard and the trackpad do not work, and the clamshell status is often switching from ON to OFF. I would like to add a contribution: replacing the whole topcase (display, and so on) did not solve the issue.

If one cannot replace such a part, does anybody know how to disable such a lid sensor via software? If not by disconnecting some cable inside?


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@gp313 - The issue is not within the case for the Hall detector is part of the main logic board (see my update above).

I think you have other problems here it would be best to create a fresh question with all of your details.


Thanks. I just read your update with the picture localising the involved sensor (perhaps it could be in a similar location for my rMBP 13)

I just wanted to confirm that the replacement of the top case has nothing to do with this issue, which - sorry to insist - seems exactly the same (with a slightly different bad behaviour of the sensor in my case: mine often switching from clamshell ON to clamshell OFF whatever is the position of the lid; while the OP’s sensor seems to be always ON). I hope that one will be able to find how to solve such an issue, at least via software.

In the meanwhile, could you please be so kind to post the line to temporary shut off all the SMC sensors? I would like to check how my macbook will act, in order to have a further confirmation. Thanks.



Sorry I don't remember exactly how I was able to boot it ignoring some sensors (including the hall effect sensor). And there is no official way of doing that... I stumble on that when I was doing some tests.

It was something like, with the battery unplugged, press and hold the power button while connecting the power cable (with the battery always unplugged). The computer should start with fans at full speed because the fans sensors (and others) are off.

I'll check my notes later, and let you know if it was different.


Thank you, Sérgio. It could be nice to also do some tests without SMC... just in order to collect a further confirmation about my hall sensor issue. As expected, unfortunately the Apple labs propose to replace the whole logic-board, which is not affordable. Thanks again.


Keep in mind running with disabled SMC logic is like running your car with no oil! It won't take long for the engine to seize up! Here you'll kill your system in short order, I would strongly recommend not doing this.


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Hi all,

I have the same problem in a macbook pro 2013 A1425. Did you solve the problem?

Fans always runs at 8000 rpm.

Please help me

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