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iMac 2017 Fan/Slow issues...

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Panicof1907

macrumors member
Original poster
Dec 19, 2020
34
1
I purchased a 2017 through Best Buy last month as my former iMac blew up.

Unfortunately, I am wondering if I discovered why the former owner had returned this computer. It looked very nice, with hardly any wear and tear, however I noticed right out the box as soon as I try to wake it up from sleep mode, the FAN turns into a rocketship and is loud and turning fast. Also, things start to slow down... Right now I am typing sooo slow.

Any ideas why this happens when I wake it up from SLEEP? kernel_task process shows over 500% and sometimes over 800%

Is this clearly a hardware error, or could it be doing something weird like indexing the spotlight?
 
Damn, I was afraid of this! No wonder it was returned! This is the 3'rd mac I've purchased in my life and each has had horrible (defective) problems. For the expensive cost of these things, this should be unacceptable!

I am assuming since I purchased it through Best-Buy (third party retailer) I can't just have it fixed at any Genius Desk? Absolutely frustrating.
 
Panicof1907 said:
Damn, I was afraid of this! No wonder it was returned! This is the 3'rd mac I've purchased in my life and each has had horrible (defective) problems. For the expensive cost of these things, this should be unacceptable!

I am assuming since I purchased it through Best-Buy (third party retailer) I can't just have it fixed at any Genius Desk? Absolutely frustrating.
Click to expand...
I would think ask Best-Buy first. Don't you have at least a 90-day warranty from them?

Sorry you have this issue. Apple may not be to blame: the former owner may have opened it, for example to upgrade HDD to SSD, and messed up a sensor (a common issue).
 
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btw, did you try resetting SMC and NVRAM? This probably won't help, but you might be lucky.

Reset the SMC of your Mac - Apple Support

The SMC is responsible for managing power on your Mac. Resetting it can resolve certain uncommon issues related to power or thermal management.
support.apple.com support.apple.com

Reset NVRAM on your Mac - Apple Support

If one or more settings stored in NVRAM don't work as expected on an Intel-based Mac, resetting NVRAM might help.
support.apple.com support.apple.com
 
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I'm back guys. In regard to the SSD theory, that is something I've wondered about myself. I recently updated an old 2011 mac and noticed the issue there with the FANs going crazy on hard-drive upgrades too. But I don't remember that throttling down the whole system?

I will have to look up this model # and try to see if they did changes, will get back to you guys on this. I COULD purchase software to try to FORCE the fans to run slower, but this in theory gives me two problems.

#1. Isn't that risky in case there is a REAL over-heat issue?
#2. Even if I can force the FANs to shut off, wouldn't the kernel_task just eat up 500 to 800% of the processing in order to force-throttle down the CPUs? How could disabling the fans prevent that?


In any case, I just did a hard-ware test right now.

There may be an issue with the System Management Controller (SMC).
Ref: PFM00G
 
You know wilberforce, that leads me to question those people who upgrade their old disc drives to SSDs. How on earth then do they get around kernel_task from doing the same? Trading off HD speed for CPU speed seems silly. I must be missing something..

That said, the plot thickens... I did some digging around this LOUD iMac.

I have a 2017 model 27" 3.4Ghz model.
The model code is iMac18,3

When I do some research this site pops up:

Lookup Mac Specs By Serial Number, Order, Model & EMC Number, Model ID @ EveryMac.com

EveryMac.com's Ultimate Mac Lookup - lookup Apple Mac, iPod, iPhone and iPad specs by serial number, order number, model number, model ID, EMC number and more.
everymac.com everymac.com

What's interesting is that supposedly this model is supposed to only have 8 Gigs ram memory, but mine here has 16. So I assume someone upgraded it on the initial order.

The hard-drive spec is off. The model on that site is supposed to only have a 1TB Fusion drive. But when I check what I have on this desk here, it is 4 TB. Either this WAS an option on order for the upgrade, or someone tampered around. Any way to tell for sure if it was a legit OPTION?

Device Name: APPLE SSD SM0128G
MEDIUM TYPE: SSD
 
If someone has opened the iMac to upgrade the HDD to SSD, a common mistake is to neglect to replace the internal temperature sensor in the HDD with an external temperature sensor for the SSD, using something like this:
eshop.macsales.com

OWC In-line Digital Thermal Sensor for 27-inch iMacs

OWC's in-line solution is the only hardware digital thermal sensor on the market allowing a third-party SATA drive to be installed in your iMac.
eshop.macsales.com eshop.macsales.com

Another common mistake is to inadvertently disturb the LCD temperature sensor while opening.
Either of these mistakes can cause the fans and kernel_task to max out.

Both of these are fixable (if this is the cause), but require surgery and diagnosis.

However, there are mixed reports on whether the SSD temperature sensor is needed or not, depending on the exact model, configuration and firmware.

Not sure why should should have to deal with it, having just bought the machine, unless you bought it "as is." In which case I hope you got a good price.
 
Last edited:
"However, there are mixed reports on whether the SSD temperature sensor is needed or not"

Damn, don't you just love it when no one can make heads or tails out of something?!

I will do some more digging around. If I can find out that the 4Terabyte SSD was a legit upgrade solution, then I'll just let Apple handle this issue. But if it was NOT a standard issue, then I guess Apple will squawk and say it's no longer covered or something.
 
I am now looking over my receipt...

Apple iMac Retina 5K, 27-inch - (2017) MNE92LL/A - 3.4GHz Intel Core i5 / 8GB RAM / 1TB Hard Drive / AMD Radeon Pro 570 4GB - Refurbished

Interesting, I got 2x the RAM memory and 4x the hard drive space than which I had ordered for here. I guess that's the good news.

Interesting... It was a marketplace order, so I can't return it to BestBuy right now if I even wanted to, as they state they are not taking returns for those orders at this time. Just not sure if that means due to the Pandemic, or other.
 
Update!

So it most definitely looks like someone has done some personal upgrading/tampering around...

The 2017 model was

Configure to Order​

ONLY up to these specs:
  • 3.4GHz
    • Magic Trackpad 2
    • Magic Keyboard with Numeric Keypad
    • 16GB or 32GB memory upgrade
    • 2TB Fusion Drive
    • 256GB, 512GB, or 1TB SSD
So, the fact I have a 4TD SSD is highly suspicious... it definitely was not a standard issue.
 
kernel_task is what shows up when your Mac starts to throttle. It's a legitimate task that should idle if everything is ok and produces "dummy load" as soon as the CPU starts overheating and therefore starts to throttle.

In other news, the 2017 iMac was never sold with a 4 TB SSD by Apple. In fact, I don't believe you can buy current iMacs with SSDs that large, as far as I know they only go up to 2 TB. The bad news is that the 2017 does not have that thermal sensor anymore and is therefore not affected by the well-known and well-documented issue that affected all previous iMacs until and including the 2015 model.

What I believe is happening in your case is a faulty sensor reporting internal overheating, which in turn causes the CPU to throttle and the fan to go bonkers. You can inspect your CPU closer using Intel's Power Gadget tool. That should provide you with more information.
 
Panicof1907 said:
So, the fact I have a 4TD SSD is highly suspicious... it definitely was not a standard issue.
Click to expand...

If it is a 3.5" SATA SSD, then it is definitely third-party and your machine was opened to install it and the temperature sensors either were damaged/removed or improperly installed.

Factory SSDs from Apple are M.2 blades and I do not believe 4TB was an option on the 2017 (I have a 1TB factory M.2 blade SSD in my 2017).
 
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Do you not have recourse with Bestbuy marketplace? It seems the computer was misrepresented, as its description is incorrect (it is described as having 1TB HDD, whereas it actually has an SSD). You should tell them you want what was described.
 
Just Simply check with any software tool brand and model of that ssd. And report It here. I would return It. It Is not a matter of warranty or return policy.
They sell an Apple which contains non-apple parts....so It Is almost fraud. There Is no time for this.....
 
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" The bad news is that the 2017 does not have that thermal sensor anymore and is therefore not affected by the well-known and well-documented issue that affected all previous iMacs until and including the 2015 model."

This is the first time I have heard of this. But I will take your word for it...

This has been frustrating and I've been doing a lot of research on it. I think at this point I will just give up... will try to see what my return options are. Probably another $100 for shipping the other way just to get rid of it and a refund :(

I bet it will be re-sold again to some poor chap. No doubt the previous owner did the same and this is why it is in my hands.

Last time I ever buy anything refurbished!
 
If you want Apple refurbs buy only from Apple with the full 12 month warranty and the opportunity to purchase additional AppleCare. You should have recourse to Consumer Law Protection as the goods do not fit the description of what was offered for sale.
 
I don't know. I've still heard so many horror stories of people buying refurbished iMacs directly from Apple as well. In any case, I have sent a reply to the re-seller. I had to keep it small to fit it in the limited window. Here's what I sent to date, and I'll keep you all updated going forward:

---

Hello my friends. I wanted to give an update on an issue with this upon arrival.

The computer seems a little different from what was listed. For example, I have 8 Gigs ram instead of 4 in this machine. Also, the hard drive is 4T instead of 1T. While this is quite generous, and I certainly would never complain about this gift, the problem is that there is a major defect in this machine.

The built-in fans in this machine tend to run at full blast continually... sometimes they stop right after a reboot, but almost always will speed up as soon as the computer is woken from asleep even if you can get them to slow down.

The activity monitor often shows Kernal_Task running at 250-800%. This is a sign the OS is trying to throttle down the computations in order to avoid over-heating. This also explains why the computer runs TERRIBLY slow when the fans are going, even if there are almost no other processes running to cause any heat. A hardware test confirms an SMC error Ref: PFM006
 
Panicof1907 said:
I've still heard so many horror stories of people buying refurbished iMacs directly from Apple as well.
Click to expand...
I have yet to hear a single horror story about Apple's Refurbished Store to date. Those things are either literally brand-new (overstock) or refurbished to like-new condition. I've purchased numerous devices through Apple's Refurbished Store and haven't been disappointed once. And even if you receive a lemon these devices come with the exact same 1-year warranty with optional AppleCare+ warrenty extension as all new devices so there's literally no difference in regard to warranty and service whatsoever.
 
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What a horrendously bad scenario, from bad to worse!

So I reshipped it back and we decided to do an exchange with the 3rd party retailer. I have just NOW received bad news and images that the iMac screen was damaged and is shattered which was due to FedEx shipping!! And this is NOT the first time those bastards have damaged one of my iMacs!

Why is it I have a disastrous feeling that I am going to have to pay for this loss/mess?! This is the horror show that just keeps on giving!

What a nightmare...
 
The defective heat sensor problem rendered my MacBook Pro (which was otherwise still working just fine) useless. It would be nice if there were a way to turn off the throttling down feature. As an alternative, does there exist an earlier version of the OS for which the throttling down feature had not yet been developed?
 
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