Step 2: is simple. Simply put clear tape or anti static tape on the logic board PCB of the original hard from the iMac . Making sure it wont touch anything, as safety.
MAKE SURE YOU PLUG IN only the temperature sensor cable FROM the iMac to the hard drive Logic board we have taped to the iMacs back housing, this is *crucial. This will make the iMac control the fan speed as normal. :)