"24 in iMac fan running constantly after replacing hard drive" için yanıtYou rock Harry. I replaced the drive in my mom's iMac (17" Intel) a while back and it was fine at first but appears the sensor failed or lost connection resulting in full speed fans. I couldn't find the problem for the life of me until I came here. Thanks to HDDFanControl it's back to normal while still protecting the machine. If you just defeat the sensor you're losing protection, HDDFanControl uses SMART to get the drive temperature and keep your machine protected. Plus you get to demo it for an hour to see if that solves you're problem or if there's more to it than that, couldn't ask for a more elegant solution.