I have an iMac 8,1 and iStat shows my fans as such: Optical Drive: 4792 rpm Hard Drive: 0 rpm CPU: 1597 rpm Here are the temp readings (in F): HD: MAC HD: 112 CPU: 108 CPU Heatsink: 104 Airport Card: 88 Ambient: 65 (more like 70) GPU: 113 GPU Diode: 133 GPU Heatsink: 113 This started a few months ago. My Mac is now out of warranty. Shortly after it went out of warranty I started having issues with the screen (wouldn't boot and had a grey screen with vertical bars) and Apple had to replace the GPU. As soon as I started having issues with the screen I noticed one of the fans running really loud. Thinking the problem was related, I just got the GPU replaced. I still have a really loud fan, but I'm not sure just how many fans my particular machine actually has. iStat shows one fan not running and another maxed out. So what issue am I actually facing before I go to open up my computer? I'm looking to replace the hard drive here soon with an SSD and I'm thinking I'll take care of the fan at the same time. I've noticed some people's fan problems being their logic board. Is this a part I can purchase myself somewhere? I've tried looking (some) but haven't had much luck. Thanks for the help.