Won't power on while battery cable is connected after fan replacement

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MacBook Pro 16" 2019

Tutoriels de réparation et informations de démontage pour le MacBook Pro 16" commercialisé en novembre 2019. Modèle A2141, EMC 3347.

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Aaron Massicotte @aaronmassicotte

Rep: 35

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Publié: 22 mars 2023

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Won't power on while battery cable is connected after fan replacement

As title says, I performed a fan replacement, but then the macbook wouldn't turn on. I followed MacBook Won't Turn On and identified that when the battery cable is removed, I can power on while the power connector is plugged in. Obviously there is no battery detected when this happens

Before the fan replacement, battery was in excellent condition and no issue

How should I fix this? Do I need to buy a new connector cable?

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So, you only replaced the fan unit you didn’t remove the battery of logic board, correct? Also which fan left or right?

Could you have damaged something in the process?

22 mars 2023 par Dan

I replaced both left and right fans at the same time.

Of course it's possible something could have been damaged, but I was very careful and followed the official guide. Nothing appeared to be out of the norm

Unfortunately, I'm noticing that when I power on (with battery disconnected) the fans ramp up to 100% very quickly, and kernel_task is using >1000% CPU. I am unable to reset PRAM/NVRAM

Official Apple fans were used for the replacement

22 mars 2023 par Aaron Massicotte

@aaronmassicotte - the fans ramping up is expected! SMC is going into CPU Safe Mode where it will do this when key sensors are lost, it will also lower the CPUs clocking as well.

What guide did you use?

22 mars 2023 par Dan

I used https://www.youtube.com/watch?v=IBnmbcZP...

So are you suggesting that in addition to the battery, a temperature sensor was also lost? Or is this simply normal behaviour if the battery is not connected?

Can confirm when running pmset -g thermlog, that CPU_Speed_Limit = 20 and CPU_Scheduler_Limit = 40

**** SMC sensors ****

CPU Thermal level: 255

GPU Thermal level: 100

IO Thermal level: 100

Fan: 5556.93 rpm

CPU die temperature: 32.57 C

GPU die temperature: 35.00 C

CPU Plimit: 40.00

GPU Plimit (Int): 15.00

Number of prochots: 0

Performance Limited Due to:

CPU LIMIT PROCHOT

GPU LIMIT PROCHOT

CU/GPU Overlap: 14.34%

Cores Active: 39.66%

GPU Active: 32.11%

Avg Num of Cores Active: 1.54

23 mars 2023 par Aaron Massicotte

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Dan @danj

Rep: 479k

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Publié: 24 mars 2023

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@aaronmassicotte - You really need to use a better tool to see all of the sensors. I would use this tool TG Pro

In any case the sensors involved are via the battery so without it your system goes into CPU Safe Mode.

As far as your original issue, I would double check your ribbon cable connections making sure they are fully inserted and straight in with the compression latch set. Could you have damaged one of the cables?

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Aha, yes this is a nice piece of software. Many thanks!

27 mars 2023 par Aaron Massicotte

So finally what happened was it was the battery ribbon connector. There was a problem with the way it was being inserted. Now everything is showing up as normal and working as intended

Awesome thanks to all the help. Very nice to have the support from a community like this :) Hopefully this thread can save some headaches from someone with a similar panic regarding the thermal throttling

27 mars 2023 par Aaron Massicotte

@aaronmassicotte - if everything is working, don’t forget to score the answer and accept it - Thanks!

27 mars 2023 par Dan

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So, you only replaced the fan unit you didn’t remove the battery of logic board, correct? Also which fan left or right?

Could you have damaged something in the process? — Dan
I replaced both left and right fans at the same time.

Of course it's possible something could have been damaged, but I was very careful and followed the official guide. Nothing appeared to be out of the norm

Unfortunately, I'm noticing that when I power on (with battery disconnected) the fans ramp up to 100% very quickly, and kernel_task is using >1000% CPU. I am unable to reset PRAM/NVRAM

Official Apple fans were used for the replacement — Aaron Massicotte
@aaronmassicotte - the fans ramping up is expected! SMC is going into CPU Safe Mode where it will do this when key sensors are lost, it will also lower the CPUs clocking as well.

What guide did you use? — Dan
I used https://www.youtube.com/watch?v=IBnmbcZP...

So are you suggesting that in addition to the battery, a temperature sensor was also lost? Or is this simply normal behaviour if the battery is not connected?

Can confirm when running pmset -g thermlog, that CPU_Speed_Limit = 20 and CPU_Scheduler_Limit = 40

**** SMC sensors ****

CPU Thermal level: 255

GPU Thermal level: 100

IO Thermal level: 100

Fan: 5556.93 rpm

CPU die temperature: 32.57 C

GPU die temperature: 35.00 C

CPU Plimit: 40.00

GPU Plimit (Int): 15.00

Number of prochots: 0

Performance Limited Due to:

CPU LIMIT PROCHOT

GPU LIMIT PROCHOT

CU/GPU Overlap: 14.34%

Cores Active: 39.66%

GPU Active: 32.11%

Avg Num of Cores Active: 1.54 — Aaron Massicotte
So finally what happened was it was the battery ribbon connector. There was a problem with the way it was being inserted. Now everything is showing up as normal and working as intended

Awesome thanks to all the help. Very nice to have the support from a community like this :) Hopefully this thread can save some headaches from someone with a similar panic regarding the thermal throttling — Aaron Massicotte
@aaronmassicotte - if everything is working, don’t forget to score the answer and accept it - Thanks! — Dan

MacBook Pro 16" 2019

Won't power on while battery cable is connected after fan replacement

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