Fan Noise After Adding SSD To Mid-2011 27" iMac

[Helmanfrow]

I apologize in advance if this has been done to death but I can't find a thread that addresses my issue specifically.

About an hour ago I followed OWC's tutorial video and installed an old Samsung EVO850 SATA 500GB SSD into a mid-2011 27" iMac i5.

I used a generic Chinese SATA cable from eBay, with no in-line or other kind of thermal sensor because I was led to believe that leaving the original HDD connected would be enough to negate any thermal sensor issues.

Yet when I powered up the machine, as soon as Mac OS (10.13.6) booted, the fans spun up to 100% and stayed there. I'm fairly certain that I reconnected all the cables I disconnected during disassembly but you know that I'm about to crack it open and double-check my work.

Presuming that there's no issue with the cabling, can anyone advise me on a course of action? I need to get these fans to spin down. I'd prefer a hardware solution but I'm okay with software if that's the best/only way.

Halp.

p.s. Mac OS sees the new drive so I'm fairly certain the cable works otherwise.

 

[4sallypat]

I had the same issue on a friend's 2011 iMac.
I think it's the thermal sensors that may have gone bad after replacing the hard drive....

I ended up using Mac Fan Control software to control the fans using the CPU diode as the temp sensor to use....

Works great!

 

[Helmanfrow]

Remember that I didn't replace the original HDD, but rather left it in place.

The fans worked properly right up until I added the SSD.
Seems awfully convenient that the sensors should die just at the point of upgrade.

That said I will be trying out some software.

 

[fhopper]

My OWC thermal sensor equipped cable failed twice. The adhesive would not hold and the fan went nuts. Be sure to clean the vents at the bottom of the case when inside... when my fans went nuts my vents were too clogged to handle the flow and the screen popped of the machine from internal pressure. Very unnerving.

 

[Helmanfrow]

My OWC thermal sensor equipped cable failed twice. The adhesive would not hold and the fan went nuts. Be sure to clean the vents at the bottom of the case when inside... when my fans went nuts my vents were too clogged to handle the flow and the screen popped of the machine from internal pressure. Very unnerving.

Yup. The first thing I did after opening the machine was to empty a can of compressed air into it. I swear I heard it go aaaaahhhhhhhh!!

But am I mistaken in understanding that, if the original drive is left in the machine, a supplemental drive doesn't need a thermal sensor?

 

[hwojtek]

I'm just as happy to use some software if that will help.

Macs Fan Control - control fans on Apple computers, also on Windows via Boot Camp

Control fans on Apple computers, also on Windows via Boot Camp. Monitoring of fan speed and temperature sensors. Solve fan noise and overheating problems, iMac HDD replacement

crystalidea.com

 

[fhopper]

Yup. The first thing I did after opening the machine was to empty a can of compressed air into it. I swear I heard it go aaaaahhhhhhhh!!

But am I mistaken in understanding that, if the original drive is left in the machine, a supplemental drive doesn't need a thermal sensor?

Just a general reflection on the question. If the old drive is still spinning and communicating with the "thermal system" then a new additional drive would add heat. If the old drive is not still spinning then the new drive would be still adding heat that is not identified as to source so the overall temp sensors would assume the roll of running the fans. In neither case does leaving the drive in help with controlling a new heat source. However it sounds to me like a wire in your harness is supposed to be returning data that is not happening so the fans are called on for lack of a controlling input. I ended up putting my spinner back in after an OS update stopped recognizing my new SSD. Now I just run the SSD hardwired as my boot drive and the old spinner as a data drive. BTW where did you put an additional drive? My SSD replacement drive went in the place of the old spinner.

 

[Helmanfrow]

Just a general reflection on the question. If the old drive is still spinning and communicating with the "thermal system" then a new additional drive would add heat. If the old drive is not still spinning then the new drive would be still adding heat that is not identified as to source so the overall temp sensors would assume the roll of running the fans. In neither case does leaving the drive in help with controlling a new heat source. However it sounds to me like a wire in your harness is supposed to be returning data that is not happening so the fans are called on for lack of a controlling input. I ended up putting my spinner back in after an OS update stopped recognizing my new SSD. Now I just run the SSD hardwired as my boot drive and the old spinner as a data drive. BTW where did you put an additional drive? My SSD replacement drive went in the place of the old spinner.

My intention is to move the OS and apps to the SSD and to keep the HDD for storage and fan noise mitigation.

I haven't yet had the opportunity to open the computer again and re-examine my handiwork, but if memory serves, the HDD's sensor is internal and it communicates thermal data over the SATA bus. The only discrete temperature cable is attached to the optical drive. I hope you're correct in that I simply neglected to seat this cable properly.

As an aside, I'd wager that a 2.5" SATA SSD's heat contribution is minuscule compared to a neigbouring HDD. Moreover, the fans kick in the moment the OS boots from a cold start. There's practically no way the SSD can reach threshold temperature that quickly.

 

[Nguyen Duc Hieu]

Consumer hard drives started including temperature sensors in 2008. Before that, PCs typically had no hard drive temperature sensors and Macs typically had a sensor bonded to the outside of the drive. Modern drives have a sensor bonded to the inside of the drive casing. Last I checked, most hard drives used thermistors because there was no device already bonded to the inside of the case and a thermistor is cheap if used alone. SSDs typically use silicon bandgap temperature sensors integrated into the controller, cheap because no additional device is needed

How do software programs determine the HDD temperature?

Some software programs can etermine the temperature of the hard drive. E.g. HWMonitor: I say that there must be a thermometer inside the HDD and the data (via SMART) is passed as regular info to th...

superuser.com

The issue is lying in how an iMac EMC read the temperature from 3rd party HDD/SSD. (it doesn't)
The solution is using 3rd software (Mac Fan Control). You can still read the HDD/SSD through this software.

 

[USB3foriMac]

I haven't yet had the opportunity to open the computer again and re-examine my handiwork, but if memory serves, the HDD's sensor is internal and it communicates thermal data over the SATA bus. The only discrete temperature cable is attached to the optical drive. I hope you're correct in that I simply neglected to seat this cable properly.

For the HDD, one pin (goes to SATA power connector pin 11) is used for thermal measurement. So it is not "communicated" over SATA bus, as it is not a digital readout. It is an analogue termperature sesonr that is measured by the SMC bus and is then communicated over SMC.

As an aside, I'd wager that a 2.5" SATA SSD's heat contribution is minuscule compared to a neigbouring HDD. Moreover, the fans kick in the moment the OS boots from a cold start. There's practically no way the SSD can reach threshold temperature that quickly.

Agreed, while many say SSDs are "hot": "hot" is relative, and the measurable heat increase is small and can easily be tolerated by the SSD as well as the system.

What your problem is: one of the many (!) temperature sensors throughout the logic board and components is likely not properly connected.
FYI: the fans have temperature sensor, ODD, SSD, graphic card, CPU, both heatsinks, power supply, and seneral other components.

So apart from removing all connectors and putting them back, check in particular the larger, stiff connector at the HDD: this is for camera and such. Remove the connector, and take a look with a magnifier at the pins of the socket. If this connector is not plugged-in straight but angled, some pins bend, causing a connection problem. So check with a magnifier that all pins are straight.

It could help to run a system monitor software to check all the temperatures. It might be able to tell you which temperature is "0degC" or "N/A". If you have not modified any temp sensor, you should get reasonable readings for all sensors. If one is not avaiable, you have the root cause of your problem.

Below is taken from the "Apple Technician Guide iMac (27-inch, Mid 2011)" which you can also find in the web or in this forum.

 

[Helmanfrow]

It could help to run a system monitor software to check all the temperatures. It might be able to tell you which temperature is "0degC" or "N/A". If you have not modified any temp sensor, you should get reasonable readings for all sensors. If one is not avaiable, you have the root cause of your problem.

I downloaded Macs Fan Control because it got the most consistent good reviews in the five minutes I spent doing research. I have to say it works a treat. I set it up with some nominal values and it happily revved the fans down to pre-SSD RPMs.

Strangely, but perhaps to your point, Nguyen Duc Hieu, the temperature report in Macs Fan Control suggests that all the sensors are working, and that all the components are well within spec, thermally speaking:

Would resetting the SMC help?

In any case, I'm sitting at the iMac in question now, typing this.
I just finished inspecting the various cables and their connections and everything seems to be seated properly. The glass is still off and the screen unfastened save for its umbilicals. I think I might disconnect the screen again and go over the connectors one last time before closing it up. That image you posted, USB3foriMac (if that even is you name) looks like it might come in handy.

PS I worked as a PC technician* for some 15+ years and I've gotta say that this is by far the most difficult machine I've ever worked on. More like a laptop than a desktop, really, service-wise.

This is my first thread on MacRumors; thanks for the gracious welcome!

 

[Helmanfrow]

I've added Macs Fan Control to my Login Items but is there any way to have it run before a user logs on?

In other news, I came across the notion that the presence of a thermal reading is not enough to quell the fans; there is also/actually a device ID whitelist embedded in the EFI.

This is a case of a lifetime non-Mac-PC user, who once laughed gleefully at all those sucker Mac-PC users, getting his comeuppance.