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."