This cable only transmits temperature data. Certain hard drive manufacturers need a different hard drive temperature cable. A bad temperature sensor could cause fans to spin out of control, or make the logic board think the hard drive is overheating.
593-1063-A 922-9223 iMac Late 2009 Mid 2010 A1312 27inch, Cable, Temp Sensor, Hard Drive, Hitachi NB-2783W This is the temp sensor for the 27" Intel iMac from Late 2009 and Mid 2010. These are specific to the hard drive manufacturer you are using. If you are upgrading your hard drive and switching to a different brand, you may need to change this sensor too. Apple part number: 922-9223, 593-1063-A