The April 2014 update of Apple's 13" MacBook Air features refreshed dual-core i5 and i7 processors, plus slightly increased battery performance.

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Possible fixes to temperature sensor prolbem

Hi to all of the ifixit crowd.

I have a early 2014 13.3'' Macbook Air that runs fan at full speed and kernel task usage is through the roof under OS X.

My mac is perfectly usable on Windows 10 although I have to used third party fan speed controller app cause MacBook air tends to run too hot with Windows 10.

From that app I can also see that few temp sensor readings are missing.

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I believe the problem is with temperature sensors or at least not getting data from them.

Can someone please try to put me to a right direction what parts could be broken or what connectors could be loose.

Could this be something simple, like trackpad cable or any other cable or is it certainly some sensor from MLB therefore the only possible fix replacing the MLB?

I'll attach my ASD test result pictures too.

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With kind regards


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2 Answers

Chosen Solution

Repairing the sensors would likely require swapping the parts from a dead logic board from the same model - at least some Macbooks (I haven't done this repair on your Air) use non-standard thermal sensors, and it's just easier swapping from a dead board. You then will want a logic board schematic for your model, which you hopefully will be able to find online, or else you'll need to reverse-engineer it.

There are also guys on eBay that specialize in repairing a few specific models of Macbook Airs and have old boards available as well as schematics they've helped develop themselves. As an owner of a shop that specializes in electronics repair it's usually cheaper for me to ship off a board that I don't have spares of to one of these guys than to get the parts, never mind the time involved in reverse engineering.

That being said, are you aware of the "fix" that involves running manual fan control (eg. smcFanControl) and unloading whatever kernel extension is pegging the kernel task? There's a writeup on the subject (dealing with an '11 MBA) here:

To see if it's a kext causing the load, as mentioned in that article boot into safe mode and see if it happens. If not, it's a kext. Locate the kext and disable.

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Walking around the problem is not a good idea! These sensors are there for a good reason.

Sadly, this looks like the logic board is damaged here (SMC services).

Did you spill something into the system or sit it down on a wet surface?

Often I see liquid damage when the system is reporting SMC thermal errors. If you did get it wet you might be able to clean up the corrosion on the logic board. Otherwise its time to either dig deeper in to the circuits using a schematic if you know how or just replace the logic board.

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