HDD Temperature sensor gone in 2011 iMac?

Working for me!

I couldn't figure out how to route the cables, but then I loosened the GPU screws (T8 and one T10) and pushed the original SATA cable underneath, which did it nicely

Gee, won't it be just quicker and safer to use this: OWC In-line Digital Thermal Sensor for iMac 2011 Hard Drive Upgrade. This works for any third party HD or SSD. Basically it replaces the internal sensor with an external one so SMC services work correctly in controlling the fans so your system doesn't over heat.

Well, also Apple has used this solution on their "SSD only" 2011 iMacs! So it is fully "Apple approved". ;) The only difference is that Apple is shorting wires 2 & 7 on the PCB side of the SATA cable. This mod here works as it should; the fans are no longer running at maximal speed. But yes, if you have the time and the chance then it is better to order the OWC adapter. That will be then a perfect and "clean" solution.

Well ... I wouldn't agree Apple supports your direction. Yes, electrically it will work but you are taking the long route. I would use the jumper block Apple offers as a spare if I was doing a SSD only setup. The OWC sensor is still the better solution as you don't need to pop the logic board forward to put in on.

based on article at Apple restricts hard drive replacements on new iMacs it's now using a 7 pin hard drive cable and apple firmware inside the hard drive. his is bad because you can't swap the hard drive with common hard drive available in the market.

Bodging together an old 2011 iMac years later and I can confirm this fix works.

$40 is expensive for the OWC Cable. Hope price drops.

@danj does it seems strange to you that only OWC comes up with alternatives to some of the stops Apple puts in their machines? Where are the competitors solutions. That cable should cost $15 or less.

No different than DeBeers diamonds ;-} They have a monopoly too.

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I do agree the cost is a bit high given what it is. The same part is used for the other configurations as well (2009 & newer 2012 systems)

Interesting idea. Is there anyone on this thread that's more technically savvy than I, that might be able to do something with this info to help us with run-away fan speeds?

I continue to be frustrated by the numerous comments above, stating that the "correct" way to deal with the situation is to install the OWC temp sensor, but one can't do that if there's no place to plug in the sensor! I would love to have someone address that point...

You don't have a 2011 model, you have a 2012 which uses a 2.5" drive whereas the 2011 uses a 3.5" drive. Which is why the OWC inline sensor won't work for you.

@macdoktor - Where did I say one or other?

Sorry, my bad. You said 2.5" drive, and my foggy brain read that as SSD. Apologies!

Btw, how its going ?

I'm going to upgrade my 21.5" Mid-2011 iMac HD to Samsung 850 EVO SSD.

If you willing to share, your experience would help people like me alot.

Start have a doubt to upgrade as Dan keep recomending OWC solution to this works..

The machine I upgraded worked fine, without any fan noise. I think your "mileage may vary", but if you open yours up, pull the stock drive, and there is no little cable wired to the jumpers on the drive, you should be okay without the OWC part.

Try it, and post back with the results!

You don't have a 2011 model, you have a 2012 which uses a 2.5" drive whereas the 2011 uses a 3.5" drive.

Hi JiClark,

Just comeback after 3 year, yeah you right it all work fine without using OWC part. Its been 3 years and it all fine. I would recommend anybody to upgrade their iMac to SSD.. its worth every penny.

Thanks @googly! I couldn't agree more.

Dude! I just used the Trial Version and it worked like charm as you said it! I will most likely purchased after the 14 days trial. Immediately solves my issue. I just put in a Firecuda 1TB because the stock HDD died. The Fan behind the HDD went berserk! Now everything is as peaceful as the frozen lake. Many thanks to you! my iMac is Mid 2011 27" EMC 2429. Have a good one guys!

Hello from Norway! I have bought a mid 2011 27" iMac where it have been innstalled a 1TB SSD together with a 3TB HDD. It is also a Mac FanControll installed. But it is the same problem with black screen on this machine. Some times I have ti restart and some times the screen have to be black before i Can log in. I am looking for a solution om this problem?

Did you set the Startup disk pref setting?

The issue is more complex!

A 2011 and older models use a 3.5" drive which requires the sensor. The 2012 & 13 27" also uses a 3.5" drive and requires the inline sensor as the drives heat needs to be dealt with. A 2012 and newer 21.5" models use a 2.5" drive. these are laptop drives which run cooler as they are slower RPM drives. Apple proposed to the standards group an update too SMART. It took awhile but the most of the current 2.5" drives incorporate the update so there is no issues.

While using a Y connector cable can resolve the need for the OWC in-line sensor adapter it should only be used when the 3.5" drive is replaced with a 2.5" SSD and nothing larger than 1 TB. 2 and larger SSD's tend to get a a bit warmer! I strongly recommend putting in the OWC in-line sensor so the system is able to aggressively cool the system when the SSD gets too warm.

2013 and newer 27" iMac's with newer firmware appear to not to need the inline sensor. I suspect this is related to the SMART update Apple was able to get in the standard. So then its a matter of the age of the drive does it offer the update or not if not you'll need the in-line sensor.

A Y cable is still a bit of a gamble. The reason it works is the grounds are all tied together so the line Apple is using is grounded (but not all Y cables do this). Which is why the sensor is ignored. Thats what Apple did just using a jumper block across the logic board header when they offered a SSD based 2011 model. A SATA cable extension most likely won't short the lines or even have all of the lines wired.

This then gets into what is the drive a HDD or a SSD as the heat each produces is higher with high performance HDD's (7200 Vs 5200 RPM). So defeating the sensor can be done it can put your system at risk! Its better to allow the system to measure the thermal load of the drive, hence supplying a thermal sensor is the smarter way to go with a replacement HDD or a large 2 TB or bigger SSD!

I really don't recommend doing this! In your case you are using 2 HDD's which run hotter than SSD's. I would strongly recommend you fix your cable (or replace it) and get the OWC inline sensor so you are assured the system is able to properly meter the thermals of your 3.5" drive.

why add the resistor instead of just cutting the wire?

cutting wire gives you "unreadable" again. Some resistance gives "some" reading to SMC. I used 100Ω because it's as low as nothing and as high as infinity depends on impedance, conductance, frequency, etc. Truth is I had this resistor and said "whatever", why not 100Ω? and voila, it worked. So I shared my discovery. You all can use the proper solution recommended by Dan, but we are still talking about old macs. Point is not immortal HDD, but a frequent backup. HDD fan in 2011 iMacs gives nothing anyway, no matter if it's 21.5 or 27" Look at the size! Only one fan which has intake from outside. The smallest one, the one which taking air from behind the desk. The worst dust that everyone ignores. Have a look at the foot of your macs. Surprised? Your macs breathing with it. There are no filters in macs vent holes. Lots of this dust stays inside and temperature sensors are powerless against this.

@danj Not 2 HDD's. Drives are in Fusion Drive. TEAM one which has 33ºC is SSD, Toshiba (21ºC) is HDD. Where is your hotter HDD?

@pete - I have no idea were you are going here, you implied you had HDD's. Even with a Fusion Drive config the issue is not the temp of the drives alone it's the systems ability to properly manage the thermals of the System.

See my notes about this subject. All are from experience and pictures included

It makes no difference the system requires a thermal sensor to work correctly.

So taking out your original HDD takes the sensor away. Replacing the drive with either a HDD, SSHD or SSD all require the OWC sensor for the system to work properly .

@Pete - The simple answer is the better answer! Cutting wires patching lines is not something many people get into here.

@danj Ok, yes, I know the system needs a thermal sensor to work correctly. But because SSDs generate less heat than the much larger HDDs with moving parts, could I get away without using the thermal cable?

It's not a question of which runs hotter. It's what the system requires for a data input.