I recently just had Apple look at my iMac, reason being for the glass to get cleaned on the inside as well as the LCD to get replaced. Waited a week, went and picked it up, only to be disappointed by the fact that the LCD wasn't replaced. Called Apple, they sent a certified technician to come install my LCD panel. Where he came from, was farther than the closest Apple store near me. Anyway, he came and replaced my LCD, and we tested it to make sure everything was good. It was, and I asked him to leave the glass on, since I was going to be cleaning the insides out. Apparently 3 years of dust accumulation looks pretty gross on the inside . I ended up taking the motherboard out, to clean the heatsinks and to reapply thermal paste on both the GPU and CPU. They did have an excess amount on, but for the most part was done A LOT better than my early 11 17" 2.3 i7. I ended up taking the hard drive out and swapping it for a 80gb Intel x-25m and tagging the temp sensor on it. After putting it all together, I noticed that the CPU fan runs around 3700 rpm. I tried resetting the SMC, no luck. I can use fan control or SMC and turn the CPU fan up, but it won't go below the 3700 mark. One thing to note, is that I have NOT put the glass back on, as I do not have any suction cups. I do know that I plugged everything in correctly, as well as taking the HDD temp sensor from the 1tb stock HD to put on the SSD I installed. So what could this be? ps. The Apple certified technician at the Apple store straight up told me that the iMacs DO NOT use thermal grease (I asked him if he could reapply some). HAHAHAHAHA what a dummie.