Rightside Fan 0rpm - Sensor Error?

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MacBook Pro 15" Retina Display Mid 2015

2.2 GHz (Turbo Boost up to 3.4 GHz), 2.5 GHz (Turbo Boost up to 3.7 GHz), or 2.8 GHz (Turbo Boost up to 4.0 GHz) quad-core Intel Core i7 processor with 6 MB shared L3 cache and an optional AMD Radeon R9 M370X dGPU.

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Mike Chalmers @mikechalmers

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Posted: Oct 19, 2020

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Rightside Fan 0rpm - Sensor Error?

Hi folks,

I have a recurring issue which is causing me problems:

My MacBook Pro mid-2015 rightside fan seems not to be working. I have used different software (Macs Fan Control, iStat) to determine this.

This causes kernel task to fill up the memory and stops me from doing the things I need to.

I previously replaced this fan and did have some success, but the issue is back.

However, when I power on with the shell open, both fans are spinning perfectly fine - so this leads me to believe a sensor is incorrectly reading the RPM of the right fan as 0, and acting accordingly, when it is in fact working.

What is my best bet to fixing this issue?

I’ve tried an SMC and PRAM reset already.

Thanks,

Hi @danj

So I followed the instructions to inspect the SMC chip and couldn’t notice anything myself, but took a few images that maybe someone else will notice something with.

However, upon reassembling the right side fan is now being measured accurately and seems to be working. BUT, the left side fan is now not working the same: It registers a slow speed every few seconds but almost immediately returns to zero.

I’ll attach stats on both fans (the previously working but not producing any RPM results right is the one reaching the top and constant speeds).

The kernal_task issue doesn’t seem to have occurred so far, so I guess this is a better situation than I was previously in.

Bottom line, what would you do at this point?

Thank you

Spoke too soon.. kernal task is still an issue.

Answer this question I have this problem too

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I would first try running the onboard diagnostics. Restart your system and press the D key. Did you get any errors?

I personally find TG Pro a more useful app than Macs Fan Control & iStat to diagnose cooling & thermal issues.

If you are seeing kernel_task process building up threads under Activity Monitor you are facing a deeper issue within SMC's sensors.

Oct 19, 2020 by DanJ

Hi Dan, thanks so much for your response.

Yes, I have run diagnostics, I got :

PPF004 with additional PPF003 errors.

I had this issue last year, replaced the fan and still it persisted - but after days or weeks it miraculously fixed itself: the fan was registering a normal RPM and no kernal_task issue.

But now it's back and I'd love to get to the bottom of it..

Oct 19, 2020 by Mike Chalmers

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I would first try running the onboard diagnostics. Restart your system and press the D key. Did you get any errors?

I personally find TG Pro a more useful app than Macs Fan Control & iStat to diagnose cooling & thermal issues.

If you are seeing kernel_task process building up threads under Activity Monitor you are facing a deeper issue within SMC's sensors. — DanJ
Hi Dan, thanks so much for your response.

Yes, I have run diagnostics, I got :

PPF004 with additional PPF003 errors.

I had this issue last year, replaced the fan and still it persisted - but after days or weeks it miraculously fixed itself: the fan was registering a normal RPM and no kernal_task issue.

But now it's back and I'd love to get to the bottom of it.. — Mike Chalmers

DanJ @danj Rep: 501.1k Self employed contract worker 35 344 977 · Answer 1 · 2020-10-19T18:13:05-07:00

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DanJ @danj

Rep: 501.1k

Self employed contract worker

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Posted: Oct 19, 2020

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I think you’ll need to do a deeper inspection of the logic board after taking it out following this guide MacBook Pro 15" Retina Display Mid 2015 Logic Board Replacement

Inspect the area around U5000 chip which is the SMC chip. I’m suspecting you either had a liquid spill which has damaged the logic in this area or you have a cold solder joint within the BGA pads of the chip.

Here’s an image of the area in question:

At this point you’ll need to carefully pull away the sealer around the chip and then using a good hot air rework station and flux hopefully you can get the cold solder joint under the chips BGA pads. Make sure you protect the other small SMD components around the chip as you don’t want to disturb them the process.

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Thanks Dan, I'll get on this. I've had a look through and one thing I'm not sure of, before I open up, is how do I know what the SMC chip is? Maybe it will be clear when I get in as I'm aware of some of the internal components but this one is a bit out of my grasp. Really appreciate your help diagnosing!

Oct 20, 2020 by Mike Chalmers

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MacBook Pro 15" Retina Display Mid 2015

Rightside Fan 0rpm - Sensor Error?

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