Macbook Air very slow and fan running at full speed

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Macbook Air very slow and fan running at full speed

Hi,

A friend recently gave me a 2018 13" Macbook Air. The battery was dead and the computer was very slow with the fan continuously running at full speed. I went through the usual procedures, resetting the NVRAM and the SMC without success. I then did a fresh install of the OS after erasing the SSD. Running AHT returned a PFM006 message (SMC issue). I ran the Activity Monitor and it showed very high (250 to 300%) Kernel_task usage. Thinking the bulging battery might be causing the problems I disconnected it, but there was no change.

Many posts I read pointed to water damage on the trackpad or the keyboard but I couldn't see any signs of that. I disconnected the trackpad/keyboard cable and used an external keyboard and mouse, but the problem remained. I read that defective temperature sensors might be the cause of the problem, but running TG Pro shows normal temperature readings for all sensors.

Thanks in advance for any suggestions !

Unit details:

Model number A1932

EMC 3184

OS 12 Monterey

MacBook Air

Posted on Oct 3, 2022 1:59 PM

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Answer 1

Top-ranking reply

lanhet Author

Level 1

5 points

Oct 16, 2022 9:15 AM in response to johndallas

Hey Johndallas !

I'm waiting for a battery that I ordered from China. I'll let you know how things turn out after I install it. From what I've managed to find out, the original 35W power supply is not sufficient to power the computer without the presence of the battery to supply current surges. What apparently happens in such cases is that the SMC sends out inaccurate information that makes the fan run at full speed and slows down the CPU.

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Answer 2

Oct 16, 2022 9:19 AM in response to lanhet

Cool yeah definately let me know how it turns out. I can get it to power on with my 100W Macbook Pro charger (with dead battery) but it's unusable as the system is soo laggy. I'm willing to buy a battery as well if it does the trick. Thanks for the reply and hope that does the trick for you (and me). :)

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Answer 3

John Galt

Level 10

146,402 points

Oct 4, 2022 7:44 AM in response to lanhet

Take your Mac to Apple and have them replace the battery: Get Support. If you do it yourself they may refuse to service that Mac.

Your Mac will not work without an operable battery.

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Answer 4

lanhet Author

Level 1

5 points

Oct 4, 2022 6:13 AM in response to John Galt

I did consider the dead or absent battery might be the source of the problem, but my 2010 MacBook Pro has been running perfectly without a battery for many years, so I wonder. I hesitate to buy a new battery to then realize the problem is elsewhere and not worth fixing.

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Answer 5

lanhet Author

Level 1

5 points

Oct 4, 2022 11:27 AM in response to John Galt

I've already pulled out the battery, so no going to Apple. In any case the cost would be well above what I'm willing to spend. The thing that puzzles me though is that my MacBook Pro works perfectly well without a battery.

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Answer 6

Oct 17, 2022 3:47 PM in response to lanhet

Hey Lanhet,

I bought a replacement battery off Amazon and got it today (50$ ish) and plugged it in and the macbook is 100% working again. No high fan, idle cpu under 1%, keyboard backlight working etc, who'd have thought that a battery could cause so much weirdness! Anyway hope you get the same results once your arrives. Thanks for sharing that tip on the battery! Glad to have a working device for a cheap/easy fix!

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Answer 7

lanhet Author

Level 1

5 points

Oct 31, 2022 7:50 AM in response to johndallas

Hi johndallas,

I finally received the battery and sure enough it did the job, computer and fan were back to normal speed.

Unfortunately, after installing a few programs I realized I had no sound from the built in speaker, I removed the back cover again and noticed I hadn't pushed the audio flat cable all the way in, simple fix. Not really... now the screen was dead... It turns out the backlight stopped working, so now I'm trying to find that problem...

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Answer 8

John Galt

Level 10

146,402 points

Oct 3, 2022 8:59 PM in response to lanhet

What did you do about the battery? Portable Macs need an operable battery to function.

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Answer 9

John Galt

Level 10

146,402 points

Oct 4, 2022 11:58 AM in response to lanhet

I know we used to be able to do that. A lot has changed in twelve years.

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Answer 10

lanhet Author

Level 1

5 points

Oct 4, 2022 12:06 PM in response to John Galt

Yes indeed. Thanks for the tips.

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Answer 11

Oct 16, 2022 8:44 AM in response to lanhet

Hey did you ever find a solution to this? I have the exact same issue currently with at 2018 Air. 100% dead battery, fan runs at full speed, system dead slow and can't see any water damage.

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