Hi All, I'm new to iMacs (after years of PC's) and a first-time poster. I will sincerely appreciate any comments/advice you can give me. I bought a new iMac online in December 2015 and picked it up at an Apple store in January 2016. The details are: 27-inch iMac with Retina 5K display / 3.3 GHz quad-core Intel Core i5, Turbo Boost up to 3.9GHz / 16GB 1867MHz DDR3 SDRAM - two 8GB / 2TB Fusion Drive Since the first time I used it, there has been a low volume, constant whirring noise coming from, I believe, one of the fans in back. However, when I'm sitting in front of the screen (about 2 feet away), this noise sounds like a high pitched insect's drone. It's still low volume, but the fact that it's constant makes me nuts. I'll add that the fans do not seem to run faster/louder than normal, which I read has been a problem with iMacs in the past. I chatted online with Apple's customer service about this, and they recommended the typical unplugging to reset the SMC. But this didn't help, so they recommended that I visit an Apple store. So I visited the same Apple store where I picked up the iMac. A guy plugged my iMac into an iPad and ran a diagnostic program for around 20 minutes, which didn't show any problem with the fans cooling the system. He also listened at the back of the iMac in the store and in the separate "Employees Only" Genius Room, but claimed he and other employees couldn't hear anything unusual. I asked him if I could take a brief video of the iMac at home, which would include the sound, and send the video by e-mail to him or another customer service person to show exactly what I'm talking about, but he said that wasn't a possibility. My only option was to bring the iMac back to the store and bring the video with me. So I'm planning to take the video and go back to the store, but I wanted to ask all of you: 1) Is this a common problem with iMacs? In a separate 2014 thread called "Retina iMac fan noise while idle," a poster mentioned, "Sometimes the iMac 5k whir on the left side. Don't know what it is." This made me wonder if it's a common problem. 2) Is the only option to fix the problem to replace the fan? That's what the Apple store guy said. But I'm wondering if this is the best way to go or if replacing the fan might lead to some new problem. Anyway, if you have any experience with this problem and ideas about what to do, please let me know.