Faulty CPU/ODD sensors or fans after Dual Drive Kit Upgrade

"This issue, caused by Apples greed in putting proprietary drives in, can be solved easily by using this:

OWC In-line Digital Thermal Sensor for iMac 2011 Hard Drive Upgrade

http://eshop.macsales.com/item/Other%20W..."

Check the LCD Thermal Sensor Cable (vertical sync cable) and the cable to your main hard drive. You didn't mention if you also changed the main hard drive or not.

"I know this posting is about 8 months old, but I have to respond to mayer's comment. It's my understanding that the drives shipped with the iMac's are not proprietary at all, no custom firmware is installed. It's the cables in which they connect the HDD to the logic board that are custom. That may be a proprietary cable, but Apple is using this method to receive more accurate heat information to control the fans for better performance in reducing heat then the old way by sticking a sensor on the outside of drive.

As for a standard in how manufactures make access to the hard drives internal heat sensor is different from company to company. That is why Apple has several different cables depending on which drive is sent out in the iMac. I for one have done the upgrade to a 2 drive setup. When I purchased my iMac it was originally shipped with a Seagate drive that later was issued a recall replacement. After having the new drive installed I just assumed the swap was with an identical drive. Now performing the upgrade, it turns out the recall was replaced with another manufacturers drive including a different heat sensor cable. I didn't have the correct cable, for this upgrade. Researched on-line the pins used for the Seagate drive and modified the cable to connect properly to the heat sensor pins on the new drive.

I then installed a SSD drive and reused the sensor that was taped to the side of the SuperDrive. Slapped the iMac back together and used Time Machine to install the backup of my original drives data to the new one. When turning on the iMac for the first time after the upgrade I noticed faster loading times not fan speeds.

By making the SSD the startup drive the benefits were instantly noticeable. The iMac used to take about 45 seconds to boot up and use, now I boot up and able to use in about 10 seconds. As for the fans, they work as intended by OS X, because I modified the custom cable to get the heat data from a drive that you can pick up at any electronic store nation wide. If you're not comfortable in modifying the cable, go on-line and order the correct one for the drive being used and you will not have any problems with the fans.

So, it's not a proprietary drive or ""greed"" that Apple went this route, but to gain a more accurate heat reading to control the fans for better heat dissipation."

"I had an interesting endeavor with a Mid 2011 iMac 27”. I wanted to replace the broken harddrive with a new 2,5” one and add an SSD on top of it. I got the cable for the second drive and was able get everything up and running - except that the fans were running at full speed shortly after switching the iMac on.

The first thing I came across was the issue with the non-standard HDD temperature reporting. I stumbled upon https://www.elvikom.pl/imac-21-5-27-blad... which describes that you can shorten two pins on the harddrive to let the iMac think temperature is normal. I did this on a Sabrent converter frame (3,5” to 2,5”) to avoid soldering directly on the harddrive. Guess what? Fans still spinning at full speed.

Then I tried the OWC OWCDIDIMacHDD11 which is similar to the solution offered by iFixit to add an external temperature sensor for the HDD. Aaaand it was still not working. Fans at full speed.

I was a bit out of ideas. Some weeks later I gave it another try. The whole time I was running the iMac with the display removed to make things easier while in repair. I had it connected to an external display. I ran the Apple Hardware Test and it showed me this error: 4SNS/1/C0000008: TL0P—124. I found out that this is a problem with the display temperature sensors. And indeed they were not shown by Macs Fan Control.

Obviously, this was due to the fact that I didn’t have the display attached, However, even after attaching it I got the same error and fans spinning at full speed. I removed the display again and found the temperature sensor on its backside. I removed its connectors and re-attached them. Then I attached the display again and tried starting the iMac without the additional OWC cable (i.e., only with the soldering solution). And it worked! Fans were quiet and I could see the display temperature sensors being shown by Macs Fan Control.

In the end, it seemed to be a problem with connectors of the display temperature sensor. So the iMac didn’t recognize them and turned on the fans. What a ride."