Chosen Solution
Hi, I just removed my old HDD, just to install an SDD in the HDD slot, and an HDD (1TB SATA on SATA-to-IDE-cart) in my Optical Slot. Everything seems to have gone smoothly, except… For seemingly no reason, my CPU fan goes to 3500 (CPU at 30-60°C), and my HDD fan to 1300 (HDD at 50°C). I think, at least the CPU fan shouldn’t do so… I already tried resetting the SMC, and reopened it to look if I maybe removed or forgot to reattach a temperature sensor, but both did not bring any solution at all. Any Ideas? Thank you!
Make sure you reconnect the heat sensor on the hdd - that could cause runaway fans. The other possibility is that those drives actually are overheating your machine. You could run a 3rd party fan app. to monitor internal temperature and see if it’s really getting that warm in there. If this Answer is helpful please remember to return and mark it Accepted.
Download SSD FanController, open it and click on Manual. Put the numbers around 1500. That’s it. The link is http://exirion.net/ssdfanctrl/. You may configure its preferences as to S.M.A.R.T. You’ll find out when you download and install it. If your issue is resolved, please come back and mark the answer as Accepted.
FIXED THE ISSUE…. This took a little time, but it was a simple fix. The LCD sensor that you have to disconnect from before removing the LCD was the issue. After receiving HIGH CPU fan speeds, I began looking at possible issues. First, I had Temperature Monitor Installed. I had all my sensors including the ambient air sensor reading. After I upgraded my HD to a SSD I started getting HIGH CPU fan speeds, but the HD and DVD fan speeds were fine. I looked at my Temperature Monitor and I noticed i had several Temperature Monitors not reading including the ambient Air Temperature (bare with me, these are steps to troubleshoot). After reseting the SMC and PRAM, still nothing. I shut down and disassembled my IMAC again. This time after i removed the LCD, I looked at the LCD cable that you must disconnect when removing the LCD and BAM, I saw the issue. The wires that connect to the Motherboard from the LCD Sensor, inherently like to lay across the screw hole the Bezel attaches to. I have a couple of pinched marked that exposed the wires and when I tighten the bezel down, it shorted the wires and caused the issue. I cut small pieces of electrical tape and covered the bare spots. When I reassembled the IMAC, i mad sure that all my BEZEL screw holes were completely clear of any wires. Once back together, I plugged in the IMAC, waited 5 Seconds and turned it on. All is well. I feel this a majority of everyones issues when they take apart their IMACS and put them back together. Hope this helps.
HDD Fan Control: http://www.hddfancontrol.com It’s designed specifically for this problem. And, instead of the terrible answer above (which sticks the fans at 1500 regardless how warm the machine is), HDD Fan Control uses the SMART sensors to ramp up the fans when needed. I really don’t understand why this program is never mentioned when someone brings up the fan problem when you change a hard drive in an iMac… but there you go.
Go to the Mac App Store and download ‘Temperature Gauge’ App to monitor your devices. Did you remount the thermal sensor onto your SSD from the old HD you took off.?
Same thing here. All fans are now continually going crazy. Everything is connected fine. I don’t get it. An SMC reset doesn’t work. PRAM doesn’t help. Makes no sense for all the fans to be going nuts. I wonder if it is related to the LCD temp sensor. I wonder if that could be making the fans ALL continually run.
As I will have access to the AppleCare Help Desk Tools soon, I’ll run a complete check and will keep you updated on this issue. Thanks for your suggestions up to now!
Anyone figure out what is causing the CPU fan to run a full speed?
Hi, Charlie, my graphic card died on my iMac 27 late 2009, I went to apple partner service here in Slovakia, and they give me back with CPU on max and sensor showing 0 rpm, another sensors like hdd and odd are okay, I think that service man some way broke my cpu sensor or You think that problem will be like on Your iMac with LCD? Thanks for answer
